Allow failure of py35-trial on Travis

Related to #1989

Author: nicoddemus

.travis.yml

@@ -22,13 +22,17 @@ env:
     - TESTENV=py27-trial
     - TESTENV=py35-pexpect
     - TESTENV=py35-xdist
-    # Disable py35-trial temporarily: #1989
-    #- TESTENV=py35-trial
+    - TESTENV=py35-trial
     - TESTENV=py27-nobyte
     - TESTENV=doctesting
     - TESTENV=freeze
     - TESTENV=docs
 
+matrix:
+  allow_failures:
+    # py35-trial failing on Linux: #1989
+    - env: TESTENV=py35-trial
+
 script: tox --recreate -e $TESTENV
 
 notifications: