UBUNTU: SAUCE: Documentation: import error c_funcptr_sig_re, c_sig_re (sphinx-doc/sphinx@0f49e30c)

Extension error:
   Could not import extension linuxdoc.cdomain  .. \
   (exception: cannot import name 'c_funcptr_sig_re' from ..

Issue: `sphinx-doc/sphinx#7421`_

.. _0f49e30c:
   https://github.com/sphinx-doc/sphinx/commit/0f49e30c51b5cc5055cda5b4b294c2dd9d1df573#r38750737

.. _sphinx-doc/sphinx#7421:
   https://github.com/sphinx-doc/sphinx/issues/7421

Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>
Link: https://github.com/return42/linuxdoc/commit/48f09de2aff80169b7b9be5b0f2431ad8954e5cc
Signed-off-by: Seth Forshee <seth.forshee@canonical.com>

Documentation/sphinx/cdomain.py

@@ -37,12 +37,29 @@ from docutils.parsers.rst import directives
 
 import sphinx
 from sphinx import addnodes
-from sphinx.domains.c import c_funcptr_sig_re, c_sig_re
 from sphinx.domains.c import CObject as Base_CObject
 from sphinx.domains.c import CDomain as Base_CDomain
 from itertools import chain
 import re
 
+# fixes https://github.com/sphinx-doc/sphinx/commit/0f49e30c51b5cc5055cda5b4b294c2dd9d1df573#r38750737
+
+# pylint: disable=invalid-name
+c_sig_re = re.compile(
+    r'''^([^(]*?)          # return type
+        ([\w:.]+)  \s*     # thing name (colon allowed for C++)
+        (?: \((.*)\) )?    # optionally arguments
+        (\s+const)? $      # const specifier
+    ''', re.VERBOSE)
+
+c_funcptr_sig_re = re.compile(
+    r'''^([^(]+?)          # return type
+        (\( [^()]+ \)) \s* # name in parentheses
+        \( (.*) \)         # arguments
+        (\s+const)? $      # const specifier
+    ''', re.VERBOSE)
+# pylint: enable=invalid-name
+
 __version__  = '1.1'
 
 # Get Sphinx version