Throw a validation error if the worksheet conversion fails

nbformat/converter.py

@@ -60,7 +60,7 @@ def convert(nb, to_version):
             if converted.get('nbformat', 1) == version:
                 raise ValueError("Failed to convert notebook from v%d to v%d." % (version, step_version))
         except AttributeError as e:
-            raise ValidationError(f"Notebook could not be converted from version {version} to version {step_version} because it's missing a key: {e}")
+            raise ValidationError("Notebook could not be converted from version {version} to version {step_version} because it's missing a key: {e}".format(version=version, step_version=step_version, e=e))
 
         # Recursively convert until target version is reached.
         return convert(converted, to_version)

nbformat/reader.py

@@ -70,7 +70,7 @@ def reads(s, **kwargs):
         try:
             return versions[major].to_notebook_json(nb_dict, minor=minor)
         except AttributeError as e:
-            raise ValidationError(f"The notebook is invalid and is missing an expected key: {e}")
+            raise ValidationError("The notebook is invalid and is missing an expected key: %s" % e)
     else:
         raise NBFormatError('Unsupported nbformat version %s' % major)
 

nbformat/v3/rwbase.py

@@ -3,8 +3,8 @@
 # Copyright (c) IPython Development Team.
 # Distributed under the terms of the Modified BSD License.
 
-
 from .._compat import encodebytes, decodebytes
+from .. import validator
 
 
 def restore_bytes(nb):
@@ -15,14 +15,17 @@ def restore_bytes(nb):
 
     Note: this is never used
     """
-    for ws in nb.worksheets:
-        for cell in ws.cells:
-            if cell.cell_type == 'code':
-                for output in cell.outputs:
-                    if "png" in output:
-                        output.png = output.png.encode("ascii", "replace")
-                    if "jpeg" in output:
-                        output.jpeg = output.jpeg.encode("ascii", "replace")
+    try:
+        for ws in nb.worksheets:
+            for cell in ws.cells:
+                if cell.cell_type == 'code':
+                    for output in cell.outputs:
+                        if "png" in output:
+                            output.png = output.png.encode("ascii", "replace")
+                        if "jpeg" in output:
+                            output.jpeg = output.jpeg.encode("ascii", "replace")
+    except KeyError as e:
+        raise validator.ValidationError("The notebook was invalid missing the key: %s" % e.message)
     return nb
 
 # output keys that are likely to have multiline values