Add tox tests & codecov github action

This commit essentially adds back tests to our CI pipeline. They were
previously dropped due to Travis pricing policy change.

This workflow utilizes a few interesting projects to make this action
easier to maintain such as the codecov github action
and the tox-gh-actions project
(https://github.com/ymyzk/tox-gh-actions)

This commit uses codecov instead of coveralls because using coveralls
directly inside GH-actions is buggy and the official coveralls action
only supports lcov reports which we can't seem to be able to generate at
the moment. For more information see the pull request that introduced
this commit

.github/workflows/tests.yml

@@ -0,0 +1,50 @@
+name: Tox tests and Codecov
+on: pull_request
+jobs:
+    run_tests:
+        runs-on: ubuntu-latest
+        strategy:
+            fail-fast: false
+            matrix:
+                python-version: [3.6, 3.7, 3.8, 3.9, pypy-3.7]
+
+        steps:
+            - name: Checkout repository
+              uses: actions/checkout@v2
+
+            - name: Set up Python ${{ matrix.python-version }}
+              uses: actions/setup-python@v2
+              with:
+                  python-version: ${{ matrix.python-version }}
+
+            - name: Install dependencies
+              run: |
+                  python -m pip install --upgrade pip
+                  pip install tox tox-gh-actions
+
+            - name: Test with tox
+              run: tox
+
+    coverage_report:
+        needs: run_tests
+        runs-on: ubuntu-latest
+        steps:
+            - name: Checkout repository
+              uses: actions/checkout@v2
+
+            - name: Install dependencies
+              run: |
+                  python -m pip install --upgrade pip
+                  pip install coverage docopt yarg requests
+
+            - name: Calculate coverage
+              run: coverage run --source=pipreqs -m unittest discover
+
+            - name: Create XML report
+              run: coverage xml
+
+            - name: Upload coverage to Codecov
+              uses: codecov/codecov-action@v2
+              with:
+                  files: coverage.xml
+                  fail_ci_if_error: true

README.rst

@@ -10,9 +10,8 @@
         :target: https://pypi.python.org/pypi/pipreqs
 
 
-.. image:: https://img.shields.io/coveralls/bndr/pipreqs.svg
-        :target: https://coveralls.io/r/bndr/pipreqs
-
+.. image:: https://codecov.io/gh/bndr/pipreqs/branch/master/graph/badge.svg?token=0rfPfUZEAX
+        :target: https://codecov.io/gh/bndr/pipreqs
 
 .. image:: https://img.shields.io/pypi/l/pipreqs.svg
         :target: https://pypi.python.org/pypi/pipreqs

tox.ini

@@ -1,6 +1,14 @@
 [tox]
 envlist = py36, py37, py38, py39, pypy3, flake8
 
+[gh-actions]
+python =
+    3.6: py36
+    3.7: py37
+    3.8: py38
+    3.9: py39
+    pypy-3.7: pypy3
+
 [testenv]
 setenv =
     PYTHONPATH = {toxinidir}:{toxinidir}/pipreqs