Exclude nbconvert testing config files from iptest interpretation.

IPython/testing/iptest.py

@@ -254,6 +254,12 b' def make_exclude():'
     exclusions.append(ipjoin('lib', 'inputhookgtk'))
     exclusions.append(ipjoin('kernel', 'zmq', 'gui', 'gtkembed'))
 
+    #Also done unconditionally, exclude nbconvert directories containing
+    #config files used to test.  Executing the config files with iptest would
+    #cause an exception.
+    exclusions.append(ipjoin('nbconvert', 'tests', 'files'))
+    exclusions.append(ipjoin('nbconvert', 'exporters', 'tests', 'files'))
+
     # These have to be skipped on win32 because the use echo, rm, cd, etc.
     # See ticket https://github.com/ipython/ipython/issues/87
     if sys.platform == 'win32':