*: move away from python_rules

python_rules is completely broken when it comes to py2/py3 support.

Here, we replace it with native python rules from new Bazel versions [1] and rules_pip for PyPI dependencies [2].

rules_pip is somewhat little known and experimental, but it seems to work much better than what we had previously.

We also unpin rules_docker and fix .bazelrc to force Bazel into Python 2 mode - hopefully, this repo will now work
fine under operating systems where `python` is python2 (as the standard dictates).

[1] - https://docs.bazel.build/versions/master/be/python.html

[2] - https://github.com/apt-itude/rules_pip

Change-Id: Ibd969a4266db564bf86e9c96275deffb9610dd44
diff --git a/.bazelrc b/.bazelrc
index 17fa9d4..3a589a2 100644
--- a/.bazelrc
+++ b/.bazelrc
@@ -1,3 +1,7 @@
+# https://github.com/bazelbuild/rules_docker/issues/842
+build --host_force_python=PY2
+test --host_force_python=PY2
+run --host_force_python=PY2
 # Required for app/gerrit/gerrit-oauth-provider
 build --workspace_status_command=./tools/workspace-status.sh
 test --build_tests_only