chore: install scandir on python 2

Install scandir on python2 to allow CI to continue until I get further
along in removing python2 code. Otherwise the coverage numbers drop
when python2 only code is not used.

.travis.yml

@@ -128,7 +128,7 @@ install:
   - if [[ $TRAVIS_PYTHON_VERSION != "3.4"* ]]; then pip install mysqlclient; fi
   # https://issues.roundup-tracker.org/issue2551267
   - if [[ $TRAVIS_PYTHON_VERSION == "3."* ]]; then pip install gpg; fi
-  - pip install psycopg2
+  - if [[ $TRAVIS_PYTHON_VERSION == "2."* ]]; then pip install scandir; fi
   - pip install redis
   - pip install pytz whoosh pyjwt requests
   - pip install jinja2