ci: Travis: add pypy3 to allowed failures temporarily (#5340)

ci: Travis: add pypy3 to allowed failures temporarily

Author: nicoddemus

.travis.yml

@@ -112,6 +112,9 @@ matrix:
   allow_failures:
     - python: '3.8-dev'
       env: TOXENV=py38-xdist
+    # Temporary (https://github.com/pytest-dev/pytest/pull/5334).
+    - env: TOXENV=pypy3-xdist
+      python: 'pypy3'
 
 before_script:
   - |