Try to execute codecov properly

Author: nicoddemus

appveyor.yml

@@ -10,6 +10,7 @@ environment:
   - TOXENV: "coverage"
   # note: please use "tox --listenvs" to populate the build matrix below
   - TOXENV: "linting"
+    PYTEST_NO_COVERAGE: "1"
   - TOXENV: "py27"
   - TOXENV: "py34"
   - TOXENV: "py35"
@@ -29,7 +30,9 @@ environment:
   - TOXENV: "py27-nobyte"
   - TOXENV: "doctesting"
   - TOXENV: "py36-freeze"
+    PYTEST_NO_COVERAGE: "1"
   - TOXENV: "docs"
+    PYTEST_NO_COVERAGE: "1"
 
 install:
   - echo Installed Pythons
@@ -41,9 +44,25 @@ install:
 
 build: false  # Not a C# project, build stuff at the test step instead.
 
+before_test:
+  - |
+    if not defined PYTEST_NO_COVERAGE (
+      set "_PYTEST_TOX_COVERAGE_RUN=coverage run --source {envsitepackagesdir}/_pytest/,%CD%/testing -m"
+      set "_PYTEST_TOX_EXTRA_DEP=coverage-enable-subprocess"
+    )
+
 test_script:
   - C:\Python36\python -m tox
 
+on_success:
+  - |
+    if not defined PYTEST_NO_COVERAGE (
+      C:\Python36\Scripts\pip install codecov
+      C:\Python36\Scripts\coverage combine
+      C:\Python36\Scripts\coverage report -m
+      C:\Python36\Scripts\codecov
+    )
+
 cache:
   - '%LOCALAPPDATA%\pip\cache'
   - '%USERPROFILE%\.cache\pre-commit'