Fix tox and readthedocs (#221)

* tox.ini: Fix broken path for --cov= argument

Broken since the move in commit d076fa2 .

* tox.yml: Stop using non-existent environment "coverage" for tox >=4.9.0

Related:
- tox-dev/tox#3089
- tox-dev/tox@2124458

* readthedocs.yml: Remove discontinued key "python.system_packages"

Error was:

> Problem in your project's configuration. Invalid configuration option
> "python.system_packages". This configuration key has been deprecated
> and removed. Refer to https://blog.readthedocs.com/use-system-packages-deprecated/
> to read more about this change and how to upgrade your config file.

Build log at https://readthedocs.org/projects/ansi2html/builds/21826996/ .

Upstream docs at https://blog.readthedocs.com/drop-support-system-packages/ .
Fix may be incomplete and may need a closer look.

.github/workflows/tox.yml

@@ -95,7 +95,7 @@ jobs:
       - name: Combine coverage data
         if: ${{ startsWith(matrix.passed_name, 'py') }}
         # produce a single .coverage file at repo root
-        run: tox -e coverage
+        run: tox -e py
 
       - name: Upload coverage data
         if: ${{ startsWith(matrix.passed_name, 'py') }}

readthedocs.yml

@@ -5,7 +5,6 @@ mkdocs:
 
 python:
   version: 3.8
-  system_packages: false
   install:
     - method: pip
       path: .

tox.ini

@@ -17,7 +17,7 @@ deps =
     pytest-cov
 sitepackages = False
 usedevelop = True
-commands = python -m pytest -ra --cov=ansi2html --no-cov-on-fail --cov-append --cov-report=xml:{toxworkdir}/coverage-{envname}.xml
+commands = python -m pytest -ra --cov=src/ --no-cov-on-fail --cov-append --cov-report=xml:{toxworkdir}/coverage-{envname}.xml
 
 [testenv:lint]
 description = Runs all linting tasks