Pin tox to < 4.0.0

Tox 4.0.0 was recently released and it has several breaking changes.
We pin to < 4.0.0 here. We are planning to move forward only on the
master charm branches.

Tox is also pinned to < 4.0.0 for stable branches in upstream
openstack-zuul-jobs as well as in zosci-config. However, the
requires= section in the charm's tox.ini file ends up installing
tox>4, wiping out the zuul-pinned tox<4 that was already installed
installed. This patch fixes that.

Additional changes included in this patch:
- Add bindep.txt to install standard binary dependencies.
- Switch charm-tools to 2.8.4 to remove ruamel requirement that
  doesn't work on Python 3.10 (required for pep8/cover).
- Pin zaza and zaza-openstack-tests to stable/yoga branch as
  stable/21.10 is no longer supported.
- Pin urllib3 in test-requirements.txt for py35 unit tests

Related-Bug: #2002788
Change-Id: Ib60536bae9fa69ec9966407dd352e521528cb6f1

bindep.txt

@@ -0,0 +1,4 @@
+libffi-dev [platform:dpkg]
+libpq-dev [platform:dpkg]
+libxml2-dev [platform:dpkg]
+libxslt1-dev [platform:dpkg]

requirements.txt

@@ -10,7 +10,7 @@ setuptools<50.0.0  # https://github.com/pypa/setuptools/commit/04e3df22df840c6bb
 
 # Build requirements
 cffi==1.14.6; python_version < '3.6'  # cffi 1.15.0 drops support for py35.
-charm-tools==2.8.3
+charm-tools==2.8.4
 
 simplejson
 

src/test-requirements.txt

@@ -8,5 +8,5 @@
 tox
 
 # Functional Test Requirements (let Zaza's dependencies solve all dependencies here!)
-git+https://github.com/openstack-charmers/zaza.git@stable/21.10#egg=zaza
-git+https://github.com/openstack-charmers/zaza-openstack-tests.git@stable/21.10#egg=zaza.openstack
+git+https://github.com/openstack-charmers/zaza.git@stable/yoga#egg=zaza
+git+https://github.com/openstack-charmers/zaza-openstack-tests.git@stable/yoga#egg=zaza.openstack

test-requirements.txt

@@ -50,3 +50,6 @@ pbr==5.6.0       # vault
 cryptography<3.4 # vault, keystone-saml-mellon
 lxml             # keystone-saml-mellon
 hvac             # vault, barbican-vault
+
+# Pin urllib3 for py35 unit tests
+urllib3<=1.26.7;python_version<'3.6'

tox.ini

@@ -23,6 +23,7 @@ requires =
   pip < 20.3
   virtualenv < 20.0
   setuptools<50.0.0
+  tox < 4.0.0
 
 # NOTE: https://wiki.canonical.com/engineering/OpenStack/InstallLatestToxOnOsci
 minversion = 3.18.0
@@ -96,7 +97,7 @@ commands = stestr run --slowest {posargs}
 [testenv:pep8]
 basepython = python3
 deps = flake8==3.9.2
-       charm-tools==2.8.3
+       charm-tools==2.8.4
 commands = flake8 {posargs} src unit_tests
 
 [testenv:func-target]