added listing of known exporters on error

IPython/nbconvert/exporters/export.py

@@ -86,7 +86,8 b' __all__ = ['
     'export_python_armor',
     'export_reveal',
     'export_rst',
-    'export_by_name'
+    'export_by_name',
+    'get_export_names'
 ]
 
 @DocDecorator
@@ -223,3 +224,10 b' def export_by_name(template_name, nb, config=None, transformers=None, filters=No'
     else:
         raise NameError("template for `%s` not found" % function_name)
 
+def get_export_names():
+    "Return a list of the currently supported export targets"
+    # grab everything after 'export_'
+    l = [x[len('export_'):] for x in __all__ if x.startswith('export_')]
+    # filter out the one method that is not a template
+    l = [x for x in l if 'by_name' not in x]
+    return sorted(l)

IPython/nbconvert/nbconvertapp.py

@@ -26,7 +26,7 b' import os'
 from IPython.config.application import Application
 from IPython.utils.traitlets import Bool, Unicode
 
-from .exporters.export import export_by_name
+from .exporters.export import export_by_name, get_export_names
 from .exporters.exporter import Exporter
 from .transformers import extractfigure
 from .utils.config import GlobalConfigurable
@@ -127,10 +127,15 b' class NbConvertApp(Application):'
         ipynb_file = (self.extra_args)[2]
         
         #Export
-        return_value = export_by_name(export_type, ipynb_file)
-        if return_value is None:
-            print("Error: '%s' template not found." % export_type)
-            return
+        try:
+            return_value = export_by_name(export_type, ipynb_file)
+        except NameError as e:
+            print("Error: '%s' exporter not found." % export_type,
+                  file=sys.stderr)
+            print("Known exporters are:",
+                  "\n\t" + "\n\t".join(get_export_names()),
+                  file=sys.stderr)
+            sys.exit(-1)
         else:
             (output, resources, exporter) = return_value