tox: Don't use distutils entrypoint for coverage

This is deprecated in pbr. While we're here, we also clean up some
formatting and remove an unnecessary MANIFEST.in file (pbr doesn't need
these)

Change-Id: I9d5023a083905da76c20bde503a6ec65f0849573
Signed-off-by: Stephen Finucane <stephenfin@redhat.com>

MANIFEST.in

@@ -1,6 +0,0 @@
-include AUTHORS
-include ChangeLog
-exclude .gitignore
-exclude .gitreview
-
-global-exclude *.pyc

tox.ini

@@ -1,17 +1,17 @@
 [tox]
 minversion = 3.1.1
 envlist = py3,pep8,docs
-ignore_basepython_conflict = True
-skipsdist = True
+ignore_basepython_conflict = true
+skipsdist = true
 
 [testenv]
 basepython = python3
 setenv =
-    VIRTUAL_ENV={envdir}
+  VIRTUAL_ENV={envdir}
 deps =
-     -c{env:TOX_CONSTRAINTS_FILE:https://opendev.org/openstack/requirements/raw/branch/master/upper-constraints.txt}
-     -r{toxinidir}/requirements.txt
-     -r{toxinidir}/test-requirements.txt
+  -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
+  -r{toxinidir}/requirements.txt
+  -r{toxinidir}/test-requirements.txt
 commands = stestr run {posargs}
 
 [testenv:pep8]
@@ -21,12 +21,20 @@ commands = pre-commit run -a
 commands = {posargs}
 
 [testenv:cover]
-commands = python setup.py test --coverage --testr-args='{posargs}'
+setenv =
+  {[testenv]setenv}
+  PYTHON=coverage run --source nova --parallel-mode
+commands =
+  coverage erase
+  stestr run {posargs}
+  coverage combine
+  coverage html -d cover
+  coverage report
 
 [testenv:docs]
 deps =
-    -c{env:TOX_CONSTRAINTS_FILE:https://opendev.org/openstack/requirements/raw/branch/master/upper-constraints.txt}
-    -r{toxinidir}/doc/requirements.txt
+  -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
+  -r{toxinidir}/doc/requirements.txt
 commands = sphinx-build -W -b html -d doc/build/doctrees doc/source doc/build/html
 
 [testenv:debug]
@@ -34,7 +42,7 @@ commands = oslo_debug_helper {posargs}
 
 [flake8]
 # E123, E125 skipped as they are invalid PEP-8.
-show-source = True
+show-source = true
 ignore = E123,E125,E129,W504
 builtins = _
 exclude=.venv,.git,.tox,dist,doc,*openstack/common*,*lib/python*,*egg,build