Add nbval to docs tests

.travis.yml

@@ -48,7 +48,14 @@ install:
 script:
     - 'if [[ $GROUP == js* ]]; then travis_retry python -m notebook.jstest ${GROUP:3}; fi'
     - 'if [[ $GROUP == python ]]; then nosetests -v --with-coverage --cover-package=notebook notebook; fi'
-    - 'if [[ $GROUP == docs ]]; then make -C docs/ html; fi'
+    - |
+      if [[ $GROUP == docs ]]; then
+        EXIT_STATUS=0
+        make -C docs/ html || EXIT_STATUS=$?
+        make -C docs/ linkcheck || EXIT_STATUS=$?
+        pytest --nbval --current-env docs || EXIT_STATUS=$?
+        exit $EXIT_STATUS
+      fi
 
 matrix:
     include:

setup.py

@@ -156,7 +156,7 @@ install_requires = [
 extras_require = {
     ':sys_platform != "win32"': ['terminado>=0.3.3'],
     'test:python_version == "2.7"': ['mock'],
-    'test': ['nose', 'coverage', 'requests', 'nose_warnings_filters'],
+    'test': ['nose', 'coverage', 'requests', 'nose_warnings_filters', 'nbval'],
     'test:sys_platform == "win32"': ['nose-exclude'],
 }