Add doc/requirements

We need to specify doc requirements in doc/requirements.txt
to avoid problems with the pip resolver [1] for the release team [2][3].
Removed specific doc requirements from test-requirements.txt.

The problem here is that this repos haven't doc/requirements.txt file
and by default in this case zuul will use the test-requirements.txt file
to
pull requirements [4].

This requirements file contains extra requirements like flake8 that
collided with those allowed in our job environment and so the new pip
resolver fails to install these requirements and the job exits in error.

This project meet the conditions leading to the bug and it already faced
it previously [1].

[1] http://lists.openstack.org/pipermail/release-job-failures/2021-January/001500.html
[2] http://lists.openstack.org/pipermail/openstack-discuss/2021-January/019611.html
[3] http://lists.openstack.org/pipermail/openstack-discuss/2021-January/019612.html
[4] https://opendev.org/zuul/zuul-jobs/src/branch/master/roles/ensure-sphinx/tasks/main.yaml#L36

NOTE: Also fix CI clear pbr constraints, relax hacking contraints,
fix H214 Use assertIn/NotIn(A, B) rather than assertTrue/False

Change-Id: Id7ed00333ba9571ef9e0d8f300714835ba63551b

doc/requirements.txt

@@ -0,0 +1,3 @@
+openstackdocstheme>=2.2.1 # Apache-2.0
+sphinx>=2.0.0,!=2.1.0 # BSD
+reno>=3.1.0 # Apache-2.0

requirements.txt

@@ -1 +0,0 @@
-pbr>=0.11,<2.0

test-requirements.txt

@@ -1,8 +1,5 @@
-hacking>=1.1.0,<1.2.0 # Apache-2.0
-openstackdocstheme>=2.2.1 # Apache-2.0
+hacking>=2.0.0
 
 oslotest
-sphinx>=2.0.0,!=2.1.0 # BSD
 testrepository>=0.0.18
-reno>=3.1.0 # Apache-2.0
 pyflakes>=2.2.0

tests/test_no_dup_filenames.py

@@ -36,6 +36,5 @@ class TestNoDupFilenames(testtools.TestCase):
                 for target in glob.iglob(target_dir):
                     short_path = target[len(element_dir) + 1:]
                     if not os.path.isdir(target):
-                        err_msg = 'Duplicate file name found %s' % short_path
-                        self.assertFalse(short_path in filenames, err_msg)
+                        self.assertNotIn(short_path, filenames)
                         filenames.append(short_path)

tox.ini

@@ -26,4 +26,6 @@ exclude = .venv,.tox,dist,*.egg,build,releasenotes
 show-source = true
 
 [testenv:releasenotes]
+deps = -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
+       -r{toxinidir}/doc/requirements.txt
 commands = bash -c tools/releasenotes_tox.sh