Move docs dependencies into package metadata and use same technique as...

Move docs dependencies into package metadata and use same technique as jaraco/skeleton to build docs in tox and rtd.

.github/workflows/python-tests.yml

@@ -55,7 +55,7 @@ jobs:
       uses: actions/cache@v1
       with:
         path: ~/.cache/pip
-        key: ${{ runner.os }}-pip-${{ hashFiles('docs/requirements.txt') }}-${{ hashFiles('setup.cfg') }}-${{ hashFiles('tox.ini') }}
+        key: ${{ runner.os }}-pip-${{ hashFiles('setup.cfg') }}
         restore-keys: |
           ${{ runner.os }}-pip-
           ${{ runner.os }}-

.readthedocs.yml

 python:
   version: 3
-  requirements_file: docs/requirements.txt
-  pip_install: false
+  extra_requirements:
+  - docs
+  pip_install: true

docs/requirements.txt

-sphinx!=1.8.0
-rst.linker>=1.9
-jaraco.packaging>=6.1
-
-setuptools>=34

setup.cfg

@@ -55,8 +55,10 @@ exclude = *.tests
 [options.extras_require]
 ssl =
     wincertstore==0.2; sys_platform=='win32'
+
 certs =
     certifi==2016.9.26
+
 tests =
     mock
     pytest-flake8
@@ -70,3 +72,8 @@ tests =
     paver; python_version>="3.6"
     futures; python_version=="2.7"
     pip>=19.1 # For proper file:// URLs support.
+
+docs =
+    sphinx
+    jaraco.packaging>=6.1
+    rst.linker>=1.9

tox.ini

@@ -44,12 +44,12 @@ skip_install=True
 commands=codecov -X gcov --file {toxworkdir}/coverage.xml
 
 [testenv:docs]
-deps = -r{toxinidir}/docs/requirements.txt
-skip_install=True
+extras =
+        docs
+        testing
+changedir = docs
 commands =
-    python -m bootstrap
-    sphinx-build -W -b html -d {envtmpdir}/doctrees docs docs/build/html
-    sphinx-build -W -b man -d {envtmpdir}/doctrees docs docs/build/man
+        python -m sphinx . {toxinidir}/build/html
 
 [coverage:run]
 source=