travis: tolerate failures on python-nightly

I'm seeing "coverage xml" fail, which indicates some internal problems in the "coverage" module that aren't our responsibility.
2017-04-23 16:53:12 -04:00 · 2017-04-23 16:53:12 -04:00 · 2d9763e013
commit 2d9763e013
parent c84939744f
1 changed files with 3 additions and 0 deletions
--- a/.travis.yml
+++ b/.travis.yml
@ -19,3 +19,6 @@ script:
  - tox -e coverage
 after_success:
  - codecov
+matrix:
+  allow_failures:
+    - python: "nightly"