Update waf.py for Sphinx 1.7 compatibility

[Richard Campbell]

sphinx-build --version in sphinx 1.7 seems to return its version information in stderr instead of stdout.

Added try/except blocks to the check_sphinx_version method to attempt to get version from sphinx.version_info then from cmd_and_log using the output-Context.BOTH parameter and finally from cmd_and_log with no additional argument.

Deleted unused import from sphinx.util.compat in rtemsdomain.py. This module was removed in sphinx 1.7.

[Richard Campbell]

Patch to close this ticket

[Richard Campbell <richard.campbell@…>]

In 2a06644/rtems-docs:

RTEMS Docs: Check sphinx version

Sphinx.util.compat module was removed at Sphinx version 1.7.
Imported module was not being used.

Closes #3311.

[Chris Johns]

I have reviewed the patch. It needs some more work.

Please do not import sphinx. This is a build system and so you either need to know the module is present, ie latex.py which abstracts the latex handling or you add proper checks for a correctly install Python sphinx module, which in this case should not be needed cause the tool should have a command to print the version. Has that changed?

Catching all exceptions like this to handle the case of a python module that is not installed is not a good idea, it may hides other issues that may appear. The previous code wrapped a single conversion line which is an accepted way to do this.

What is wrong with asking Sphinx for it's version?

Why require 2 calls to get the version?

[Richard Campbell]

Improved patch based on Chris' comments

[Chris Johns]

Excellent and thank you for the prompt follow up. Please push to master.

[Richard Campbell]

Deleted import of Sphinx
Ask Sphinx for its version with a single call.
Check both stdout and stderr for version string.
Wrap a single conversion line as was done in previous code.