DOC/BLD: Travis doc build notebook dependencies (pandas-dev#13493)

Added notebook deps for travis doc build.

Author: Tom Augspurger

ci/requirements-2.7_DOC_BUILD.run

@@ -1,7 +1,9 @@
 ipython
+ipykernel
 sphinx
 nbconvert
 nbformat
+notebook
 matplotlib
 scipy
 lxml

doc/make.py

@@ -193,7 +193,8 @@ def html():
                 executed = execute_nb(nb, nb + '.executed', allow_errors=True,
                                       kernel_name=kernel_name)
                 convert_nb(executed, nb.rstrip('.ipynb') + '.html')
-            except (ImportError, IndexError):
+            except (ImportError, IndexError) as e:
+                print(e)
                 print("Failed to convert %s" % nb)
 
     if os.system('sphinx-build -P -b html -d build/doctrees '