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I'm developing a web app for Google App Engine in Python on Windows 10. Everything was working fine when my main.py was just serving templates. 

import os
import urllib
from google.appengine.api import users
import jinja2
import webapp2

JINJA_ENVIRONMENT = jinja2.Environment(
    loader=jinja2.FileSystemLoader(os.path.dirname(__file__)),
    extensions=['jinja2.ext.autoescape'],
    autoescape=True)

But then I tried to add cloud storage, and got import errors no matter what library I tried. So I removed those references from main.py, and now I get an error with jinja2, which had been working fine!

ImportError: No module named jinja2

I don't remember everything I tried, but here's what I do know:

  • jinja2 is installed; attempts to pip install/upgrade says it's already installed and up-to-date, and I see it in c:\python27\lib\site-packages.
  • PYTHONPATH=C:\python27;c:\python27\lib;C:\Python27\DLLS for system and user.
  • At one point I had installed GoogleAppEngineCloudStorageClient with PIP into my app's lib directory per this. It didn't work (the module failed to import), so I also tried adding sys.path.append(os.path.join(os.path.dirname(__file__), "lib")) but it didn't help. I think this is when I started getting the jinja2 import error. So I removed the statement from main.py. Still getting the jinja2 import error. I tried pip uninstall GoogleAppEngineCloudStorageClient but it said it wasn't installed, so I tried just deleting the lib directory. Still getting the jinja2 import error.
  • Have tried restarting the service and rebooting my machine.

EDIT:

I stripped main.py all the way to the new project template,

import webapp2

class MainHandler(webapp2.RequestHandler):
    def get(self):
        self.response.write('Hello world!')

app = webapp2.WSGIApplication([
    ('/', MainHandler)
], debug=True)

and now I get an import error for webapp2:

ImportError: No module named webapp2

EDIT 2:

By inserting this at the top of my main.py,

import sys
print sys.path

I can see the wrong path for all the google packages:

'C:\\Program Files (x86)\\Google\\lib\\webapp2-2.5.2', 
'C:\\Program Files (x86)\\Google\\lib\\pycrypto-2.6', 
'C:\\Program Files (x86)\\Google\\lib\\jinja2-2.6', 
'C:\\Program Files (x86)\\Google\\lib\\markupsafe-0.15', 
'C:\\Program Files (x86)\\Google\\lib\\setuptools-0.6c11', 
'C:\\Program Files (x86)\\Google\\lib\\protorpc-1.0', 
'C:\\Program Files (x86)\\Google\\lib\\webob-1.1.1', 
'C:\\Program Files (x86)\\Google\\lib\\yaml-3.10'

They are actually in C:\Program Files (x86)\Google\google_appengine\lib

I don't know why I didn't have this problem before I tried to install that one package, but this may be related to a reported google issue.

JackOfAll
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  • What does the `libraries` section of your `app.yaml` look like? – mgilson Jun 20 '16 at 23:31
  • @mgilson libraries: - name: webapp2 version: "2.5.2" - name: pycrypto version: latest - name: jinja2 version: latest – JackOfAll Jun 20 '16 at 23:36
  • I should clarify that it works fine when I deploy it. It is only running it locally that fails. BTW, I have tried repairing the app engine sdk and python installations and it still fails. – JackOfAll Jun 21 '16 at 01:18
  • After UNINSTALLING the app engine sdk 1.9.38 and reinstalling version 1.9.36 the import error went away. I was also able to reinstall the cloud storage library as described above and it works with my live CS when deployed. So the issue may be a combination of the app engine cloud storage client and sdk v 1.9.38, related to google issue https://code.google.com/p/googleappengine/issues/detail?id=12963. Someone added an answer to this effect but it seems to have disappeared. – JackOfAll Jun 21 '16 at 05:14
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    I just undeleted it - I misinterpreted your comment as the post not answering your problem :) – Dan Cornilescu Jun 21 '16 at 16:41

2 Answers2

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Update: the issue was fixed in SDK version 1.9.40.

There is a GAE issue causing exactly this behaviour introduced in SDK version 1.9.37, see "ImportError: No module named webapp2" after Linux SDK upgrade (1.9.35 -> 1.9.38).

If your SDK version is 1.9.37 or 1.9.38 downgrade to 1.9.36, which you can find here. At least until the fix gets released.

Community
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Dan Cornilescu
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  • I mentioned that issue above, but didn't think it was quite the same because I've been running on 1.9.37-8 for six weeks with no such issues. Also removing protobuf didn't help. I'm going to try uninstalling and reinstalling. – JackOfAll Jun 21 '16 at 03:33
  • Google agrees it is the same issue and merge it in. – JackOfAll Jun 21 '16 at 21:14
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Summary:

The webapp2 and jinja2 import errors are caused by sys.path corruption, a result of a GAE defect present in versions 1.9.37 or 1.9.38. It only impacts development; deployed versions should work. It can occur immediately upon upgrading or after attempting to install other items.

Solutions:

  • Downgrading the AppEngineSDK to 1.9.36 worked for me.
  • The GAE defect will be fixed at some point after 1.9.38. Check for Issue 12963 for status.
  • Per Google issue 13084, another workaround is to manually patch sys.path in appengine_config.py. Docs here.
JackOfAll
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