Getting error "ImportError: Could not find 'input_readers' on path 'map reduce'" trying to start mapReduce job - google-app-engine

Question

I'm getting this error... "ImportError: Could not find 'input_readers' on path 'map reduce'" when trying to Run my map reduce job via the http://localhost:8080/mapreduce launcher page.
It looks like my problem is similar to this post, AppEngine mapper API import error. Unfortunately, no definitive answers were given.
I've simplified it down to this tiny testmapreduce.py:
from google.appengine.ext import db
class TestEntity(db.Model):
value = db.StringProperty()
def mapperhandler(test):
print test.value
return
And my mapreduce.yaml:
mapreduce:
- name: Simplest MapReduce
mapper:
handler: testmapreduce.mapperhandler
input_reader: mapreduce.input_readers.DatastoreInputReader
params:
- name: entity_kind
default: testmapreduce.TestEntity
One possible clue is the presence of __init__.py has no effect (whether in the project root, the mapreduce directory, or both). I'm sure I'm making a beginner mistake, but over the last couple of days I have read every bit of documentation, and all the examples I can find. Thanks.
UPDATE:
I get the same error trying to invoke it via...
control.start_map(
"Give awards",
"testmapreduce.mapperhandler",
"mapreduce.input_readers.DatastoreInputReader",
{"entity_kind": "testmapreduce.TestEntity"},
shard_count=10)
UPDATE:
As requested, the stack trace -- let me know what else would be helpful...
ERROR 2011-10-16 17:09:27,216 _webapp25.py:464] Could not find 'input_readers' on path 'mapreduce'
Traceback (most recent call last):
File "/Develop/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/google/appengine/ext/webapp/_webapp25.py", line 701, in __call__
handler.get(*groups)
File "/Users/lc/PycharmProjects/mrtest/testmapreduce.py", line 22, in get
shard_count=10) # handle web form test interface
File "/Users/lc/PycharmProjects/mrtest/mapreduce/control.py", line 94, in start_map
transactional=transactional)
File "/Users/lc/PycharmProjects/mrtest/mapreduce/handlers.py", line 811, in _start_map
mapper_input_reader_class = mapper_spec.input_reader_class()
File "/Users/lc/PycharmProjects/mrtest/mapreduce/model.py", line 393, in input_reader_class
return util.for_name(self.input_reader_spec)
File "/Users/lc/PycharmProjects/mrtest/mapreduce/util.py", line 94, in for_name
module = for_name(module_name, recursive=True)
File "/Users/lc/PycharmProjects/mrtest/mapreduce/util.py", line 102, in for_name
short_name, module_name))
ImportError: Could not find 'input_readers' on path 'mapreduce'
INFO 2011-10-16 22:09:27,253 dev_appserver.py:4247] "GET /giveawards HTTP/1.1" 500 -

Answer 1

This problem turned out to be that I was using the 2.7 version of the Python Interpreter in my local environment. When I switched to 2.5, it works fine.