Start testing PyPy

Author: Diego Argueta

.travis.yml

@@ -9,9 +9,8 @@ python:
   - "3.6"
   - "3.7"
   - "3.8-dev"
-# TODO (dargueta): Enable these once we figure out FTP timing issues in PyPy tests
-#  - 'pypy'
-#  - 'pypy3.5-7.0'
+  - 'pypy'
+  - 'pypy3.5-7.0'  # Need 7.0+ due to a bug in earlier versions that broke our tests.
 
 matrix:
   include:
@@ -22,6 +21,10 @@ matrix:
       python: '3.7'
       env: TOXENV=lint
 
+  allow_failures:
+    - python: pypy
+    - python: pypy3.5-7.0
+
 before_install:
   - pip install -U tox tox-travis
   - pip --version