Lint the integration tests with Python 3

The integration tests under 'tests/integration' are Python 3 only.
Flake8 will fail on Python 3 syntax when running under Python 2, but for
now we wouldn't like to change this, in order to keep Python 2
compatibility of the code base.

To work around the above, set up a separate tox environment to lint the
integration tests, and exclude linting the integration tests when the
rest of the code is checked.

Signed-off-by: Hunor Csomortáni <csomh@redhat.com>

docker/test-py3.sh

@@ -22,4 +22,4 @@ sed -i \
 
 # Since tox seems to ignore `usedevelop` when we have `sitepackages` on, we have to run it manually
 python3 setup.py develop --no-deps
-/usr/bin/tox -e flake8,py3 "$@"
+/usr/bin/tox -e flake8,py3,intflake "$@"

tox.ini

@@ -4,17 +4,12 @@
 # and then run "tox" from this directory.
 
 [tox]
-envlist = flake8, py27, py3
+envlist = flake8, intflake, py27, py3
 
 [flake8]
 ignore = E731,W503
 max-line-length = 100
-exclude =
-    ./.tox
-    ./.git
-    ./module_build_service/migrations
-    ./build
-    ./.env
+exclude = .tox,.git,module_build_service/migrations,build,.env
 
 [testenv]
 usedevelop = true
@@ -49,7 +44,16 @@ commands =
 basepython = python2
 skip_install = true
 deps = flake8
-commands = flake8
+# doing this until --extend-exclude support becomes available
+# https://flake8.readthedocs.io/en/latest/user/options.html#cmdoption-flake8-extend-exclude
+commands = flake8 --exclude={[flake8]exclude},tests/integration
+
+[testenv:intflake]
+basepython = python3
+skip_install = true
+sitepackages = false
+deps = flake8
+commands = flake8 tests/integration
 
 [testenv:bandit]
 basepython = python2