Incorporating PEP8 checking on PRs.

.drone.yml

@@ -42,7 +42,7 @@ build:
   # https://github.com/reddit/docker-reddit-py
   # Dependency changes in the install scripts can be optionally mirrored to the
   # image for speedups, but abstaining from doing so won't break the builds.
-  image: reddit/reddit-py:2.7.6-v1
+  image: reddit/reddit-py:2.7.6-v2
   environment:
     DEBIAN_FRONTEND: noninteractive
   commands:
@@ -50,6 +50,8 @@ build:
     - install/drone.sh
     - cd r2
     - nosetests -v .
+    - cd ..
+    - ./scripts/stylecheck_git_diff.sh
 
 # These plugins are triggered after a build failure/success.
 notify:

scripts/stylecheck_git_diff.sh

@@ -0,0 +1,37 @@
+#!/usr/bin/env bash
+###############################################################################
+# git diff style checker
+# ----------------------
+# This script runs a style check within our Drone setup, or within the
+# `drone exec` runner.
+#
+# Since the codebase has a substantial body of non-conformant code, style
+# checks are only ran on the diffs (compared to master). As a consequence of
+# this, style checks also only run on non-master branches.
+###############################################################################
+
+if [[ ${CI_BRANCH} = "master" ]]; then
+    echo "Skipping style checks on commit(s) to the master branch."
+    exit 0
+fi
+
+if [[ ${CI_REPO:=} = "" ]]; then
+    # This assumed to be `drone exec`.
+    echo "Running style checks on staged local changes..."
+    git diff --cached | pep8 --diff
+else
+    echo "Running style checks within Drone..."
+    git fetch --no-tags --depth=10 origin master
+    git diff origin/${CI_BRANCH} origin/master | pep8 --diff
+fi
+error_encountered=$?
+
+if [[ ${error_encountered} = 1 ]]; then
+    echo "!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!"
+    echo "pep8 issues found. reddit follows pep8: https://github.com/reddit/styleguide"
+    echo "              Please commit a fix or ignore inline with: noqa"
+    echo "!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!"
+    exit 1
+fi
+
+echo "Style checks passed. Good jerb!"