[SPARK-19505][PYTHON] AttributeError on Exception.message in Python3

## What changes were proposed in this pull request?

Added `util._message_exception` helper to use `str(e)` when `e.message` is unavailable (Python3).  Grepped for all occurrences of `.message` in `pyspark/` and these were the only occurrences.

## How was this patch tested?

- Doctests for helper function

## Legal

This is my original work and I license the work to the project under the project’s open source license.

Author: David Gingrich <david@textio.com>

Closes apache#16845 from dgingrich/topic-spark-19505-py3-exceptions.

dev/sparktestsupport/modules.py

@@ -340,6 +340,7 @@ def __hash__(self):
         "pyspark.profiler",
         "pyspark.shuffle",
         "pyspark.tests",
+        "pyspark.util",
     ]
 )
 

python/pyspark/broadcast.py

@@ -21,6 +21,7 @@
 from tempfile import NamedTemporaryFile
 
 from pyspark.cloudpickle import print_exec
+from pyspark.util import _exception_message
 
 if sys.version < '3':
     import cPickle as pickle
@@ -82,7 +83,8 @@ def dump(self, value, f):
         except pickle.PickleError:
             raise
         except Exception as e:
-            msg = "Could not serialize broadcast: " + e.__class__.__name__ + ": " + e.message
+            msg = "Could not serialize broadcast: %s: %s" \
+                  % (e.__class__.__name__, _exception_message(e))
             print_exec(sys.stderr)
             raise pickle.PicklingError(msg)
         f.close()

python/pyspark/cloudpickle.py

@@ -56,6 +56,7 @@
 import traceback
 import weakref
 
+from pyspark.util import _exception_message
 
 if sys.version < '3':
     from pickle import Pickler
@@ -152,13 +153,13 @@ def dump(self, obj):
         except pickle.PickleError:
             raise
         except Exception as e:
-            if "'i' format requires" in e.message:
-                msg = "Object too large to serialize: " + e.message
+            emsg = _exception_message(e)
+            if "'i' format requires" in emsg:
+                msg = "Object too large to serialize: %s" % emsg
             else:
-                msg = "Could not serialize object: " + e.__class__.__name__ + ": " + e.message
+                msg = "Could not serialize object: %s: %s" % (e.__class__.__name__, emsg)
             print_exec(sys.stderr)
             raise pickle.PicklingError(msg)
-
 
     def save_memoryview(self, obj):
         """Fallback to save_string"""

python/pyspark/util.py

@@ -0,0 +1,45 @@
+# -*- coding: utf-8 -*-
+#
+# Licensed to the Apache Software Foundation (ASF) under one or more
+# contributor license agreements.  See the NOTICE file distributed with
+# this work for additional information regarding copyright ownership.
+# The ASF licenses this file to You under the Apache License, Version 2.0
+# (the "License"); you may not use this file except in compliance with
+# the License.  You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+__all__ = []
+
+
+def _exception_message(excp):
+    """Return the message from an exception as either a str or unicode object.  Supports both
+    Python 2 and Python 3.
+
+    >>> msg = "Exception message"
+    >>> excp = Exception(msg)
+    >>> msg == _exception_message(excp)
+    True
+
+    >>> msg = u"unicöde"
+    >>> excp = Exception(msg)
+    >>> msg == _exception_message(excp)
+    True
+    """
+    if hasattr(excp, "message"):
+        return excp.message
+    return str(excp)
+
+
+if __name__ == "__main__":
+    import doctest
+    (failure_count, test_count) = doctest.testmod()
+    if failure_count:
+        exit(-1)