diff --git a/src/__mocks__/fetch.ts b/src/__mocks__/fetch.ts
index 2e693866..493f72f2 100644
--- a/src/__mocks__/fetch.ts
+++ b/src/__mocks__/fetch.ts
@@ -1,16 +1,31 @@
 "use strict";
 
-let mockResponses: { [url: string]: string } = {};
+type Json = { [key: string]: unknown };
+type MockResponse = { status: number; statusText: string; ok: boolean; body: Json };
+
+let mockResponses: { [url: string]: Partial<MockResponse> } = {};
+
+const defaultMockResponseParams = {
+  status: 200,
+  statusText: "OK",
+  ok: true,
+};
 
 export default async function fetch(url: string) {
   const mockResponse = mockResponses[url];
   if (mockResponse) {
-    return { json: () => mockResponse };
+    const fullMockResponse = { ...defaultMockResponseParams, ...mockResponse };
+    return {
+      status: fullMockResponse.status,
+      statusText: fullMockResponse.statusText,
+      ok: fullMockResponse.ok,
+      json: () => Promise.resolve(fullMockResponse.body),
+    };
   }
   throw new Error(`Unknown URL: ${url}`);
 }
 
-export function __setMockResponses(newMockResponses: { [url: string]: string }) {
+export function __setMockResponses(newMockResponses: { [url: string]: Partial<MockResponse> }) {
   mockResponses = newMockResponses;
 }
 
diff --git a/src/changelog.spec.ts b/src/changelog.spec.ts
index 7d312813..460d7dd4 100644
--- a/src/changelog.spec.ts
+++ b/src/changelog.spec.ts
@@ -69,17 +69,21 @@ describe("Changelog", () => {
 
       const usersCache = {
         "https://api.github.com/users/test-user": {
-          login: "test-user",
-          html_url: "https://github.com/test-user",
-          name: "Test User",
+          body: {
+            login: "test-user",
+            html_url: "https://github.com/test-user",
+            name: "Test User",
+          },
         },
       };
       const issuesCache = {
         "https://api.github.com/repos/lerna/lerna-changelog/issues/2": {
-          number: 2,
-          title: "This is the commit title for the issue (#2)",
-          labels: [{ name: "Type: New Feature" }, { name: "Status: In Progress" }],
-          user: usersCache["https://api.github.com/users/test-user"],
+          body: {
+            number: 2,
+            title: "This is the commit title for the issue (#2)",
+            labels: [{ name: "Type: New Feature" }, { name: "Status: In Progress" }],
+            user: usersCache["https://api.github.com/users/test-user"].body,
+          },
         },
       };
       require("./fetch").__setMockResponses({
@@ -107,24 +111,32 @@ describe("Changelog", () => {
 
       const usersCache = {
         "https://api.github.com/users/test-user": {
-          login: "test-user",
-          html_url: "https://github.com/test-user",
-          name: "Test User",
+          body: {
+            login: "test-user",
+            html_url: "https://github.com/test-user",
+            name: "Test User",
+          },
         },
         "https://api.github.com/users/test-user-1": {
-          login: "test-user-1",
-          html_url: "https://github.com/test-user-1",
-          name: "Test User 1",
+          body: {
+            login: "test-user-1",
+            html_url: "https://github.com/test-user-1",
+            name: "Test User 1",
+          },
         },
         "https://api.github.com/users/test-user-2": {
-          login: "test-user-2",
-          html_url: "https://github.com/test-user-2",
-          name: "Test User 2",
+          body: {
+            login: "test-user-2",
+            html_url: "https://github.com/test-user-2",
+            name: "Test User 2",
+          },
         },
         "https://api.github.com/users/user-bot": {
-          login: "user-bot",
-          html_url: "https://github.com/user-bot",
-          name: "User Bot",
+          body: {
+            login: "user-bot",
+            html_url: "https://github.com/user-bot",
+            name: "User Bot",
+          },
         },
       };
       require("./fetch").__setMockResponses(usersCache);
diff --git a/src/changelog.ts b/src/changelog.ts
index f52e4bee..75f2aa49 100644
--- a/src/changelog.ts
+++ b/src/changelog.ts
@@ -215,17 +215,19 @@ export default class Changelog {
   private async fillInPackages(commits: CommitInfo[]) {
     progressBar.init("Mapping commits to packages…", commits.length);
 
-    await pMap(
-      commits,
-      async (commit: CommitInfo) => {
-        commit.packages = await this.getListOfUniquePackages(commit.commitSHA);
-
-        progressBar.tick();
-      },
-      { concurrency: 5 }
-    );
-
-    progressBar.terminate();
+    try {
+      await pMap(
+        commits,
+        async (commit: CommitInfo) => {
+          commit.packages = await this.getListOfUniquePackages(commit.commitSHA);
+
+          progressBar.tick();
+        },
+        { concurrency: 5 }
+      );
+    } finally {
+      progressBar.terminate();
+    }
   }
 
   private async fillInContributors(releases: Release[]) {
diff --git a/src/cli.ts b/src/cli.ts
index 8a0ea4ce..fb6ff387 100644
--- a/src/cli.ts
+++ b/src/cli.ts
@@ -88,5 +88,7 @@ export async function run() {
     } else {
       console.log(chalk.red(e.stack));
     }
+
+    process.exitCode = 1;
   }
 }
diff --git a/src/functional/markdown-empty.spec.ts b/src/functional/markdown-empty.spec.ts
index 76f16758..c14923ec 100644
--- a/src/functional/markdown-empty.spec.ts
+++ b/src/functional/markdown-empty.spec.ts
@@ -50,48 +50,60 @@ const listOfFileForEachCommit: { [id: string]: string[] } = {
 
 const usersCache = {
   "https://api.github.com/users/luke": {
-    login: "luke",
-    html_url: "https://github.com/luke",
-    name: "Luke Skywalker",
+    body: {
+      login: "luke",
+      html_url: "https://github.com/luke",
+      name: "Luke Skywalker",
+    },
   },
   "https://api.github.com/users/vader": {
-    login: "vader",
-    html_url: "https://github.com/vader",
-    name: "Darth Vader",
+    body: {
+      login: "vader",
+      html_url: "https://github.com/vader",
+      name: "Darth Vader",
+    },
   },
   "https://api.github.com/users/gtarkin": {
-    login: "gtarkin",
-    html_url: "https://github.com/gtarkin",
-    name: "Governor Tarkin",
+    body: {
+      login: "gtarkin",
+      html_url: "https://github.com/gtarkin",
+      name: "Governor Tarkin",
+    },
   },
 };
 const issuesCache = {
   "https://api.github.com/repos/lerna/lerna-changelog/issues/1": {
-    number: 1,
-    title: "feat: May the force be with you",
-    labels: [{ name: "Type: New Feature" }],
-    pull_request: {
-      html_url: "https://github.com/lerna/lerna-changelog/pull/1",
+    body: {
+      number: 1,
+      title: "feat: May the force be with you",
+      labels: [{ name: "Type: New Feature" }],
+      pull_request: {
+        html_url: "https://github.com/lerna/lerna-changelog/pull/1",
+      },
+      user: usersCache["https://api.github.com/users/luke"],
     },
-    user: usersCache["https://api.github.com/users/luke"],
   },
   "https://api.github.com/repos/lerna/lerna-changelog/issues/2": {
-    number: 2,
-    title: "chore: Terminate her... immediately!",
-    labels: [{ name: "Type: Breaking Change" }],
-    pull_request: {
-      html_url: "https://github.com/lerna/lerna-changelog/pull/2",
+    body: {
+      number: 2,
+      title: "chore: Terminate her... immediately!",
+      labels: [{ name: "Type: Breaking Change" }],
+      pull_request: {
+        html_url: "https://github.com/lerna/lerna-changelog/pull/2",
+      },
+      user: usersCache["https://api.github.com/users/gtarkin"],
     },
-    user: usersCache["https://api.github.com/users/gtarkin"],
   },
   "https://api.github.com/repos/lerna/lerna-changelog/issues/3": {
-    number: 3,
-    title: "fix: Get me the rebels base!",
-    labels: [{ name: "Type: Bug" }],
-    pull_request: {
-      html_url: "https://github.com/lerna/lerna-changelog/pull/3",
+    body: {
+      number: 3,
+      title: "fix: Get me the rebels base!",
+      labels: [{ name: "Type: Bug" }],
+      pull_request: {
+        html_url: "https://github.com/lerna/lerna-changelog/pull/3",
+      },
+      user: usersCache["https://api.github.com/users/vader"],
     },
-    user: usersCache["https://api.github.com/users/vader"],
   },
 };
 
diff --git a/src/functional/markdown-full.spec.ts b/src/functional/markdown-full.spec.ts
index 95a70bb3..4c9cb799 100644
--- a/src/functional/markdown-full.spec.ts
+++ b/src/functional/markdown-full.spec.ts
@@ -141,109 +141,139 @@ const listOfFileForEachCommit: { [id: string]: string[] } = {
 
 const usersCache = {
   "https://api.github.com/users/luke": {
-    login: "luke",
-    html_url: "https://github.com/luke",
-    name: "Luke Skywalker",
+    body: {
+      login: "luke",
+      html_url: "https://github.com/luke",
+      name: "Luke Skywalker",
+    },
   },
   "https://api.github.com/users/princess-leia": {
-    login: "princess-leia",
-    html_url: "https://github.com/princess-leia",
-    name: "Princess Leia Organa",
+    body: {
+      login: "princess-leia",
+      html_url: "https://github.com/princess-leia",
+      name: "Princess Leia Organa",
+    },
   },
   "https://api.github.com/users/vader": {
-    login: "vader",
-    html_url: "https://github.com/vader",
-    name: "Darth Vader",
+    body: {
+      login: "vader",
+      html_url: "https://github.com/vader",
+      name: "Darth Vader",
+    },
   },
   "https://api.github.com/users/gtarkin": {
-    login: "gtarkin",
-    html_url: "https://github.com/gtarkin",
-    name: "Governor Tarkin",
+    body: {
+      login: "gtarkin",
+      html_url: "https://github.com/gtarkin",
+      name: "Governor Tarkin",
+    },
   },
   "https://api.github.com/users/han-solo": {
-    login: "han-solo",
-    html_url: "https://github.com/han-solo",
-    name: "Han Solo",
+    body: {
+      login: "han-solo",
+      html_url: "https://github.com/han-solo",
+      name: "Han Solo",
+    },
   },
   "https://api.github.com/users/chewbacca": {
-    login: "chewbacca",
-    html_url: "https://github.com/chewbacca",
-    name: "Chwebacca",
+    body: {
+      login: "chewbacca",
+      html_url: "https://github.com/chewbacca",
+      name: "Chwebacca",
+    },
   },
   "https://api.github.com/users/rd-d2": {
-    login: "rd-d2",
-    html_url: "https://github.com/rd-d2",
-    name: "R2-D2",
+    body: {
+      login: "rd-d2",
+      html_url: "https://github.com/rd-d2",
+      name: "R2-D2",
+    },
   },
   "https://api.github.com/users/c-3po": {
-    login: "c-3po",
-    html_url: "https://github.com/c-3po",
-    name: "C-3PO",
+    body: {
+      login: "c-3po",
+      html_url: "https://github.com/c-3po",
+      name: "C-3PO",
+    },
   },
 };
 const issuesCache = {
   "https://api.github.com/repos/lerna/lerna-changelog/issues/1": {
-    number: 1,
-    title: "feat: May the force be with you",
-    labels: [{ name: "Type: New Feature" }],
-    pull_request: {
-      html_url: "https://github.com/lerna/lerna-changelog/pull/1",
+    body: {
+      number: 1,
+      title: "feat: May the force be with you",
+      labels: [{ name: "Type: New Feature" }],
+      pull_request: {
+        html_url: "https://github.com/lerna/lerna-changelog/pull/1",
+      },
+      user: usersCache["https://api.github.com/users/luke"].body,
     },
-    user: usersCache["https://api.github.com/users/luke"],
   },
   "https://api.github.com/repos/lerna/lerna-changelog/issues/2": {
-    number: 2,
-    title: "chore: Terminate her... immediately!",
-    labels: [{ name: "Type: Breaking Change" }],
-    pull_request: {
-      html_url: "https://github.com/lerna/lerna-changelog/pull/2",
+    body: {
+      number: 2,
+      title: "chore: Terminate her... immediately!",
+      labels: [{ name: "Type: Breaking Change" }],
+      pull_request: {
+        html_url: "https://github.com/lerna/lerna-changelog/pull/2",
+      },
+      user: usersCache["https://api.github.com/users/gtarkin"].body,
     },
-    user: usersCache["https://api.github.com/users/gtarkin"],
   },
   "https://api.github.com/repos/lerna/lerna-changelog/issues/3": {
-    number: 3,
-    title: "fix: Get me the rebels base!",
-    labels: [{ name: "Type: Bug" }],
-    pull_request: {
-      html_url: "https://github.com/lerna/lerna-changelog/pull/3",
+    body: {
+      number: 3,
+      title: "fix: Get me the rebels base!",
+      labels: [{ name: "Type: Bug" }],
+      pull_request: {
+        html_url: "https://github.com/lerna/lerna-changelog/pull/3",
+      },
+      user: usersCache["https://api.github.com/users/vader"].body,
     },
-    user: usersCache["https://api.github.com/users/vader"],
   },
   "https://api.github.com/repos/lerna/lerna-changelog/issues/4": {
-    number: 4,
-    title: "fix: RRRAARRWHHGWWR",
-    labels: [{ name: "Type: Bug" }, { name: "Type: Maintenance" }],
-    pull_request: {
-      html_url: "https://github.com/lerna/lerna-changelog/pull/4",
+    body: {
+      number: 4,
+      title: "fix: RRRAARRWHHGWWR",
+      labels: [{ name: "Type: Bug" }, { name: "Type: Maintenance" }],
+      pull_request: {
+        html_url: "https://github.com/lerna/lerna-changelog/pull/4",
+      },
+      user: usersCache["https://api.github.com/users/chewbacca"].body,
     },
-    user: usersCache["https://api.github.com/users/chewbacca"],
   },
   "https://api.github.com/repos/lerna/lerna-changelog/issues/5": {
-    number: 5,
-    title: "feat: I am your father",
-    labels: [{ name: "Type: New Feature" }],
-    pull_request: {
-      html_url: "https://github.com/lerna/lerna-changelog/pull/5",
+    body: {
+      number: 5,
+      title: "feat: I am your father",
+      labels: [{ name: "Type: New Feature" }],
+      pull_request: {
+        html_url: "https://github.com/lerna/lerna-changelog/pull/5",
+      },
+      user: usersCache["https://api.github.com/users/vader"].body,
     },
-    user: usersCache["https://api.github.com/users/vader"],
   },
   "https://api.github.com/repos/lerna/lerna-changelog/issues/6": {
-    number: 6,
-    title: "refactor: he is my brother",
-    labels: [{ name: "Type: Enhancement" }],
-    pull_request: {
-      html_url: "https://github.com/lerna/lerna-changelog/pull/6",
+    body: {
+      number: 6,
+      title: "refactor: he is my brother",
+      labels: [{ name: "Type: Enhancement" }],
+      pull_request: {
+        html_url: "https://github.com/lerna/lerna-changelog/pull/6",
+      },
+      user: usersCache["https://api.github.com/users/princess-leia"].body,
     },
-    user: usersCache["https://api.github.com/users/princess-leia"],
   },
   "https://api.github.com/repos/lerna/lerna-changelog/issues/7": {
-    number: 7,
-    title: "feat: that is not how the Force works!",
-    labels: [{ name: "Type: New Feature" }, { name: "Type: Enhancement" }],
-    pull_request: {
-      html_url: "https://github.com/lerna/lerna-changelog/pull/7",
+    body: {
+      number: 7,
+      title: "feat: that is not how the Force works!",
+      labels: [{ name: "Type: New Feature" }, { name: "Type: Enhancement" }],
+      pull_request: {
+        html_url: "https://github.com/lerna/lerna-changelog/pull/7",
+      },
+      user: usersCache["https://api.github.com/users/han-solo"].body,
     },
-    user: usersCache["https://api.github.com/users/han-solo"],
   },
 };
 
@@ -351,4 +381,54 @@ describe("createMarkdown", () => {
       expect(markdown).toMatchSnapshot();
     });
   });
+
+  describe("authentication", () => {
+    describe("when github token is not valid", () => {
+      const badCredentials = {
+        message: "Bad credentials",
+        documentation_url: "https://developer.github.com/v3",
+      };
+      beforeEach(() => {
+        require("../git").changedPaths.mockImplementation((sha: string) => listOfFileForEachCommit[sha]);
+        require("../git").lastTag.mockImplementation(() => "v8.0.0");
+        require("../git").listCommits.mockImplementation(() => listOfCommits);
+        require("../git").listTagNames.mockImplementation(() => listOfTags);
+
+        const unauthorized = {
+          status: 401,
+          statusText: "Unauthorized",
+          ok: false,
+          body: badCredentials,
+        };
+        require("../fetch").__setMockResponses({
+          ...usersCache,
+          ...Object.keys(issuesCache).reduce(
+            (unauthorizedIssues, issue) => ({
+              ...unauthorizedIssues,
+              [issue]: unauthorized,
+            }),
+            {}
+          ),
+        });
+      });
+      afterEach(() => {
+        jest.resetAllMocks();
+      });
+      it("should abort with a proper error message", async () => {
+        const MockedChangelog = require("../changelog").default;
+        const changelog = new MockedChangelog();
+        expect.assertions(2);
+        try {
+          await changelog.createMarkdown();
+        } catch (error) {
+          expect(error).toEqual(
+            expect.objectContaining({ message: expect.stringContaining("Fetch error: Unauthorized") })
+          );
+          expect(error).toEqual(
+            expect.objectContaining({ message: expect.stringContaining(JSON.stringify(badCredentials)) })
+          );
+        }
+      });
+    });
+  });
 });
diff --git a/src/github-api.ts b/src/github-api.ts
index d0450597..b89ab717 100644
--- a/src/github-api.ts
+++ b/src/github-api.ts
@@ -61,7 +61,11 @@ export default class GithubAPI {
         Authorization: `token ${this.auth}`,
       },
     });
-    return res.json();
+    const parsedResponse = await res.json();
+    if (res.ok) {
+      return parsedResponse;
+    }
+    throw new ConfigurationError(`Fetch error: ${res.statusText}.\n${JSON.stringify(parsedResponse)}`);
   }
 
   private getAuthToken(): string {