allow nightly version to fail

Author: willingc

.travis.yml

@@ -13,26 +13,28 @@ env:
     - GROUP=python
 matrix:
   exclude:
-  - python: 3.6
-    env: GROUP=docs
-  - python: 3.7
-    env: GROUP=docs
-  - python: 3.8
-    env: GROUP=docs
-  - python: nightly
-    env: GROUP=docs
-  - python: 3.6
-    env: GROUP=nbextensions
-  - python: 3.7
-    env: GROUP=nbextensions
-  - python: 3.8
-    env: GROUP=nbextensions
-  - python: nightly
-    env: GROUP=nbextensions
+    - python: 3.6
+      env: GROUP=docs
+    - python: 3.7
+      env: GROUP=docs
+    - python: 3.8
+      env: GROUP=docs
+    - python: nightly
+      env: GROUP=docs
+    - python: 3.6
+      env: GROUP=nbextensions
+    - python: 3.7
+      env: GROUP=nbextensions
+    - python: 3.8
+      env: GROUP=nbextensions
+    - python: nightly
+      env: GROUP=nbextensions
+  allow_failures:
+    - python: nightly
 addons:
   apt:
     packages:
-    - pandoc
+      - pandoc
   firefox: latest
 before_install:
   - pip install -U pip wheel setuptools