Fix functional tests and docs generation

First, fix test_help(). A commit[1], which first appeared in Python
3.10, changes the output of the help feature of argparse. Options used
to be in a section named "Optional arguments:", and they are now in a
section named "Options:".

Second, tox 4 changes the behaviour of tox, and
{toxinidir}/requirements.txt is no longer installed automagically in the
docs virtual environment. This causes autodoc to fail on some imports.
We explicitely add {toxinidir}/requirements.txt to the list of
dependencies to fix this issue.

These issues should be fixed in separate patches, but since they both
block the CI, they depend on each other.

[1] https://github.com/python/cpython/pull/23858

Change-Id: Ia7866390b31f469bdea95624325a13aaf45a496e
Closes-Bug: #2002566

glanceclient/tests/functional/v1/test_readonly_glance.py

@@ -51,6 +51,13 @@ class SimpleReadOnlyGlanceClientTest(base.ClientTestBase):
 
         commands = []
         cmds_start = lines.index('Positional arguments:')
+        try:
+            # Starting in Python 3.10, argparse displays options in the
+            # "Options:" section...
+            cmds_end = lines.index('Options:')
+        except ValueError:
+            # ... but before Python 3.10, options were displayed in the
+            # "Optional arguments:" section.
             cmds_end = lines.index('Optional arguments:')
         command_pattern = re.compile(r'^ {4}([a-z0-9\-\_]+)')
         for line in lines[cmds_start:cmds_end]:

glanceclient/tests/functional/v2/test_readonly_glance.py

@@ -71,6 +71,13 @@ class SimpleReadOnlyGlanceClientTest(base.ClientTestBase):
 
         commands = []
         cmds_start = lines.index('Positional arguments:')
+        try:
+            # Starting in Python 3.10, argparse displays options in the
+            # "Options:" section...
+            cmds_end = lines.index('Options:')
+        except ValueError:
+            # ... but before Python 3.10, options were displayed in the
+            # "Optional arguments:" section.
             cmds_end = lines.index('Optional arguments:')
         command_pattern = re.compile(r'^ {4}([a-z0-9\-\_]+)')
         for line in lines[cmds_start:cmds_end]:

tox.ini

@@ -54,7 +54,9 @@ commands =
 
 [testenv:docs]
 basepython = python3
-deps = -r{toxinidir}/doc/requirements.txt
+deps =
+  -r{toxinidir}/requirements.txt
+  -r{toxinidir}/doc/requirements.txt
 commands =
   sphinx-build -W -b html doc/source doc/build/html
   sphinx-build -W -b man doc/source doc/build/man