Fix PYTHONPATH is not set when running collectstatic (#637)

* Fix PYTHONPATH is not set when running collectstatic

* update changelog

Signed-off-by: Kenneth Reitz <me@kennethreitz.org>

* Update CHANGELOG.md

CHANGELOG.md

 # Python Buildpack Changelog
 
+# 125
+
+Set `PYTHONPATH` during collectstatic runs.
+
 # 124
 
 Update buildpack to automatically install [dev-packages] (Pipenv) during Heroku CI builds.

bin/steps/collectstatic

@@ -30,6 +30,7 @@ if [ ! "$DISABLE_COLLECTSTATIC" ] && [ -f "$MANAGE_FILE" ] && [ "$DJANGO_INSTALL
     puts-step "$ python $MANAGE_FILE collectstatic --noinput"
 
     # Run collectstatic, cleanup some of the noisy output.
+    export PYTHONPATH=.
     python "$MANAGE_FILE" collectstatic --noinput --traceback 2>&1 | sed '/^Post-processed/d;/^Copying/d;/^$/d' | indent
     COLLECTSTATIC_STATUS="${PIPESTATUS[0]}"