Integrate 'pre-commit'

This nifty tool provides a extensible way to configure pre-commit hooks
to do everything from running linters to spellchecking [1] and has
already been adopted by a few OpenStack projects [2]. Let's start using
it as a faster, more automatic alternative to the 'fast8' tox target and
iterate on it as we find more things to use it for. The 'fast8' target
is not deprecated though a note is included for end-users to alert them
to this great new tool.

Note that the 'check-executables-have-shebangs' actually failed and
highlighted that the 'contributor/development-environment.rst' document
was marked as executable when it shouldn't have been. This is corrected.

[1] https://pre-commit.com/
[2] https://review.opendev.org/#/q/file:.pre-commit-config.yaml

Change-Id: I256e75eceeb3495dce04885ca42d16adb4160cf3
Signed-off-by: Stephen Finucane <sfinucan@redhat.com>

tools/flake8wrap.sh

@@ -13,8 +13,15 @@ if test "x$1" = "x-HEAD" ; then
     shift
     files=$(git diff --name-only HEAD~1 | tr '\n' ' ')
     echo "Running flake8 on ${files}"
+    echo ""
+    echo "Consider using the 'pre-commit' tool instead."
+    echo ""
+    echo "    pip install --user pre-commit"
+    echo "    pre-commit install --allow-missing-config"
+    echo ""
     diff -u --from-file /dev/null ${files} | flake8 --diff "$@"
 else
     echo "Running flake8 on all files"
+    echo ""
     exec flake8 "$@"
 fi