fix jpeg/jpg typo in ExtractOutput

IPython/nbconvert/preprocessors/extractoutput.py

@@ -35,7 +35,7 b' class ExtractOutputPreprocessor(Preprocessor):'
     output_filename_template = Unicode(
         "{unique_key}_{cell_index}_{index}{extension}", config=True)
 
-    extract_output_types = Set({'png', 'jpg', 'svg', 'application/pdf'}, config=True)
+    extract_output_types = Set({'png', 'jpeg', 'svg', 'application/pdf'}, config=True)
 
     def preprocess_cell(self, cell, resources, cell_index):
         """
@@ -71,7 +71,7 b' class ExtractOutputPreprocessor(Preprocessor):'
                     data = out[out_type]
 
                     #Binary files are base64-encoded, SVG is already XML
-                    if out_type in {'png', 'jpg', 'application/pdf'}:
+                    if out_type in {'png', 'jpeg', 'application/pdf'}:
 
                         # data is b64-encoded as text (str, unicode)
                         # decodestring only accepts bytes