feat(dev): enable gitpod development

Use the initalization phase to install all of the Python versions
and run the tests on startup, making subsequent test runs faster.

Signed-off-by: Mike Fiedler <miketheman@gmail.com>

.gitpod.yml

@@ -0,0 +1,23 @@
+# See https://www.gitpod.io/docs/references/gitpod-yml for full reference
+
+tasks:
+  - name: Setup Development and run Tests
+
+    init: |
+      # Upgrade pyenv itself
+      pyenv update
+
+      export PY_VERSIONS="3.7 3.8 3.9 3.10"
+
+      # Install all supported Python versions
+      for py in $PY_VERSIONS;
+        do pyenv install "$py":latest --skip-existing ;
+      done
+
+      # Make versions available via $PATH, exclude GitPod default
+      pyenv global $(pyenv versions --bare | grep -v 3.8.12)
+
+      # Install `tox` test orchestrator
+      pip install tox
+
+    command: tox

pyproject.toml

@@ -2,6 +2,10 @@
 requires = ["setuptools>=40.8.0", "wheel", "bleach>=2.1.0", "docutils>=0.13.1", "Pygments>=2.5.1"]
 build-backend = "setuptools.build_meta:__legacy__"
 
+# TODO: Remove when https://github.com/mgedmin/check-manifest/pull/155 released
+[tool.check-manifest]
+ignore = [".gitpod.yml"]
+
 [tool.mypy]
 strict = true
 warn_unused_configs = true