Fixes issue #1070, Sphinx fails python 2.7

Fixes an issue where Sphinx fails with python < 3.5 because of an update
to docutils to 0.18. Limited docutils for python 3.5.

We also set some of the Sphinx limits from pywbem dev_requirements.txt.

Author: KSchopmeyer

dev-requirements.txt

@@ -63,7 +63,13 @@ PyYAML>=5.2,<5.3; python_version == '3.4'
 PyYAML>=5.3.1; python_version > '3.4'
 
 # Sphinx (no imports, invoked via sphinx-build script):
-Sphinx>=1.7.6
+# Keep in sync with rtd-requirements.txt
+# Sphinx 2.0.0 removed support for Python 2.7 and 3.4
+# Sphinx 4.0.0 breaks autodocsumm (pywbem issue #2697)
+Sphinx>=1.7.6,<2.0.0; python_version <= '3.4'
+Sphinx>=3.0.4,<4.0.0; python_version >= '3.5'
+# Issue #1070 docutils v=0.18/Sphinx < 1 incompatibility
+docutils<0.18; python_version <= '3.4'
 sphinx-git>=10.1.1
 GitPython>=2.1.1;
 sphinxcontrib-fulltoc>=1.2.0

docs/changes.rst

@@ -63,6 +63,8 @@ Released: not yet
 * Fixed install error of wrapt 1.13.0 on Python 2.7 on Windows due to lack of
   MS Visual C++ 9.0 on GitHub Actions, by pinning it to <1.13.
 
+* Fixed issue with Sphinx and python 2.7. (see issue 1070)
+
 **Enhancements:**
 
 * Added a 'pywbemlistener' command for running and managing WBEM listeners.

rtd-requirements.txt

@@ -6,5 +6,8 @@ ply>=3.10
 PyYAML>=3.13
 # M2Crypto>=0.30.1  # we cannot install M2Crypto because RTD does not have Swig
 Sphinx>=1.7.6
+Sphinx>=3.0.4,<4.0.0; python_version >= '3.5'
+# Issue #1070 docutils v=0.18/Sphinx < 1 incompatibility
+docutils<0.18; python_version <= '3.4'
 sphinx-git>=10.1.1
 sphinxcontrib-fulltoc>=1.2.0