Fix File.valid() and clarify File behavior in error cases

.ci-dockerfiles/alpine-llvm-3.9.1/Dockerfile

@@ -12,3 +12,8 @@ RUN apk add --update \
   libexecinfo-dev \
   coreutils \
   linux-headers
+
+# add user pony in order to not run tests as root
+RUN adduser -D -s /bin/sh -h /home/pony -g root pony
+USER pony
+WORKDIR /home/pony

.ci-dockerfiles/alpine-llvm-3.9.1/README.md

@@ -6,10 +6,12 @@ docker build -t ponylang/ponyc-ci:alpine-llvm-3.9.1 .
 
 # Run image to test
 
-Will get you a bash shell in the image to try cloning Pony into where you can test a build to make sure everything will work before pushing
+Use the [CircleCI CLI](https://circleci.com/docs/2.0/local-cli/) to run the CI jobs using this image
+from the ponyc project root:
 
 ```bash
-docker run --name ponyc-ci-alpine-llvm-391 --rm -i -t ponylang/ponyc-ci:alpine-llvm-3.9.1 bash
+circleci build --job alpine-llvm-391-debug
+circleci build --job alpine-llvm-391-release
 ```
 
 # Push to dockerhub

.ci-dockerfiles/llvm-3.9.1/Dockerfile

@@ -28,3 +28,8 @@ RUN wget ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/pcre2-10.21.tar.b
  && make install \
  && cd .. \
  && rm -rf pcre2-10.21*
+
+# add user pony in order to not run tests as root
+RUN useradd -ms /bin/bash -d /home/pony -g root pony
+USER pony
+WORKDIR /home/pony

.ci-dockerfiles/llvm-3.9.1/README.md

@@ -6,10 +6,12 @@ docker build -t ponylang/ponyc-ci:llvm-3.9.1 .
 
 # Run image to test
 
-Will get you a bash shell in the image to try cloning Pony into where you can test a build to make sure everything will work before pushing
+Use the [CircleCI CLI](https://circleci.com/docs/2.0/local-cli/) to run the CI job using this image
+from the ponyc project root:
 
 ```bash
-docker run --name ponyc-ci-llvm-391 --rm -i -t ponylang/ponyc-ci:llvm-3.9.1 bash
+circleci build --job llvm-391-debug
+circleci build --job llvm-391-release
 ```
 
 # Push to dockerhub

.ci-dockerfiles/llvm-4.0.1/Dockerfile

@@ -28,3 +28,8 @@ RUN wget ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/pcre2-10.21.tar.b
  && make install \
  && cd .. \
  && rm -rf pcre2-10.21*
+
+# add user pony in order to not run tests as root
+RUN useradd -ms /bin/bash -d /home/pony -g root pony
+USER pony
+WORKDIR /home/pony

.ci-dockerfiles/llvm-4.0.1/README.md

@@ -6,10 +6,12 @@ docker build -t ponylang/ponyc-ci:llvm-4.0.1 .
 
 # Run image to test
 
-Will get you a bash shell in the image to try cloning Pony into where you can test a build to make sure everything will work before pushing
+Use the [CircleCI CLI](https://circleci.com/docs/2.0/local-cli/) to run the CI job using this image
+from the ponyc project root:
 
 ```bash
-docker run --name ponyc-ci-llvm-401 --rm -i -t ponylang/ponyc-ci:llvm-4.0.1 bash
+circleci build --job llvm-401-debug
+circleci build --job llvm-401-release
 ```
 
 # Push to dockerhub

.ci-dockerfiles/llvm-5.0.1/Dockerfile

@@ -16,3 +16,8 @@ RUN apt-get update \
   zlib1g-dev \
  && wget -O - http://llvm.org/releases/${LLVM_VERSION}/clang+llvm-${LLVM_VERSION}-x86_64-linux-gnu-ubuntu-16.04.tar.xz \
  | tar xJf - --strip-components 1 -C /usr/local/ clang+llvm-${LLVM_VERSION}-x86_64-linux-gnu-ubuntu-16.04
+
+# add user pony in order to not run tests as root
+RUN useradd -ms /bin/bash -d /home/pony -g root pony
+USER pony
+WORKDIR /home/pony

.ci-dockerfiles/llvm-5.0.1/README.md

@@ -5,11 +5,13 @@ docker build -t ponylang/ponyc-ci:llvm-5.0.1 .
 ```
 
 # Run image to test
-
-Will get you a bash shell in the image to try cloning Pony into where you can test a build to make sure everything will work before pushing
+```
+Use the [CircleCI CLI](https://circleci.com/docs/2.0/local-cli/) to run the CI job using this image
+from the ponyc project root:
 
 ```bash
-docker run --name ponyc-ci-llvm-501 --rm -i -t ponylang/ponyc-ci:llvm-5.0.1 bash
+circleci build --job llvm-501-debug
+circleci build --job llvm-501-release
 ```
 
 # Push to dockerhub

.ci-dockerfiles/llvm-6.0.0/Dockerfile

@@ -25,3 +25,8 @@ RUN apt-get update \
  && rm -rf /tmp/pcre* \
  && wget -O - http://releases.llvm.org/${LLVM_VERSION}/clang+llvm-${LLVM_VERSION}-x86_64-linux-gnu-ubuntu-14.04.tar.xz \
  | tar xJf - --no-same-owner --strip-components 1 -C /usr/local/ clang+llvm-${LLVM_VERSION}-x86_64-linux-gnu-ubuntu-14.04
+
+# add user pony in order to not run tests as root
+RUN useradd -ms /bin/bash -d /home/pony -g root pony
+USER pony
+WORKDIR /home/pony

.ci-dockerfiles/llvm-6.0.0/README.md

@@ -6,10 +6,12 @@ docker build -t ponylang/ponyc-ci:llvm-6.0.0 .
 
 # Run image to test
 
-Will get you a bash shell in the image to try cloning Pony into where you can test a build to make sure everything will work before pushing
+Use the [CircleCI CLI](https://circleci.com/docs/2.0/local-cli/) to run the CI job using this image
+from the ponyc project root:
 
 ```bash
-docker run --name ponyc-ci-llvm-600 --rm -i -t ponylang/ponyc-ci:llvm-6.0.0 bash
+circleci build --job llvm-600-debug
+circleci build --job llvm-600-release
 ```
 
 # Push to dockerhub

.ci-dockerfiles/openssl-1.1.0/Dockerfile

@@ -24,3 +24,8 @@ RUN apt-get update \
    && make install \
    && cd .. \
    && rm -rf openssl-1.1.0*
+
+# add user pony in order to not run tests as root
+RUN useradd -ms /bin/bash -d /home/pony -g root pony
+USER pony
+WORKDIR /home/pony

.ci-dockerfiles/openssl-1.1.0/README.md

@@ -6,10 +6,11 @@ docker build -t ponylang/ponyc-ci:openssl-1.1.0 .
 
 # Run image to test
 
-Will get you a bash shell in the image to try cloning Pony into where you can test a build to make sure everything will work before pushing
+Use the [CircleCI CLI](https://circleci.com/docs/2.0/local-cli/) to run the CI job using this image
+from the ponyc project root:
 
 ```bash
-docker run --name ponyc-ci-openssl-110 --rm -i -t ponylang/ponyc-ci:openssl-1.1.0 bash
+circleci build --job openssl-110
 ```
 
 # Push to dockerhub

.ci-dockerfiles/shellcheck/README.md

@@ -6,10 +6,11 @@ docker build -t ponylang/ponyc-ci:shellcheck .
 
 # Run image to test
 
-Will get you a bash shell in the image to try cloning Pony into where you can test a build to make sure everything will work before pushing
+Use the [CircleCI CLI](https://circleci.com/docs/2.0/local-cli/) to run the CI job using this image
+from the ponyc project root:
 
 ```bash
-docker run --name ponyc-ci-shellcheck --rm -i -t ponylang/ponyc-ci:shellcheck bash
+circleci build --job validate-shell-scripts
 ```
 
 # Push to dockerhub

.circleci/config.yml

@@ -15,66 +15,77 @@ jobs:
   llvm-600-debug:
     docker:
       - image: ponylang/ponyc-ci:llvm-6.0.0
+        user: pony
     steps:
       - checkout
       - run: make test-ci config=debug default_pic=true
   llvm-600-release:
     docker:
       - image: ponylang/ponyc-ci:llvm-6.0.0
+        user: pony
     steps:
       - checkout
       - run: make test-ci config=release default_pic=true
   llvm-501-debug:
     docker:
       - image: ponylang/ponyc-ci:llvm-5.0.1
+        user: pony
     steps:
       - checkout
       - run: make test-ci config=debug default_pic=true
   llvm-501-release:
     docker:
       - image: ponylang/ponyc-ci:llvm-5.0.1
+        user: pony
     steps:
       - checkout
       - run: make test-ci config=release default_pic=true
   llvm-401-debug:
     docker:
       - image: ponylang/ponyc-ci:llvm-4.0.1
+        user: pony
     steps:
       - checkout
       - run: make test-ci config=debug default_pic=true
   llvm-401-release:
     docker:
       - image: ponylang/ponyc-ci:llvm-4.0.1
+        user: pony
     steps:
       - checkout
       - run: make test-ci config=release default_pic=true
   llvm-391-debug:
     docker:
       - image: ponylang/ponyc-ci:llvm-3.9.1
+        user: pony
     steps:
       - checkout
       - run: make test-ci config=debug default_pic=true
   llvm-391-release:
     docker:
       - image: ponylang/ponyc-ci:llvm-3.9.1
+        user: pony
     steps:
       - checkout
       - run: make test-ci config=release default_pic=true
   openssl-110:
     docker:
       - image: ponylang/ponyc-ci:openssl-1.1.0
+        user: pony
     steps:
       - checkout
       - run: make test-ci default_ssl=openssl_1.1.0 default_pic=true
   alpine-llvm-391-debug:
     docker:
       - image: ponylang/ponyc-ci:alpine-llvm-3.9.1
+        user: pony
     steps:
       - checkout
       - run: make test-ci config=debug default_pic=true
   alpine-llvm-391-release:
     docker:
       - image: ponylang/ponyc-ci:alpine-llvm-3.9.1
+        user: pony
     steps:
       - checkout
       - run: make test-ci config=release default_pic=true