How to use a library that imports memcache in App Engine
To further clarify jayhendren's answer - if you are planning to use GAE's memcache service, you must use 
from google.appengine.api import memcache
you cannot use an open source memcache library. The only scenario where you could use the standard python memcache lib is if you were running your own memcache service somewhere (e.g. on Compute Engine) and you wanted to connect out to that over a socket. I'm guessing you're not doing that.
Assuming you want to use GAE's built in memcache service:  since there are differences between the API defined by GAE's memcache lib and the standard python memcache libs, you will have to make some minor changes to memorised so that it can successfully talk to the GAE memcache library. For the most part though the developer facing functionality is the same as the standard python lib. If you get it working, let us know!
I want to use a library (memorised) that uses memcache like this: import memcache
Now on App Engine, memcache must be imported like this: from google.appengine.api import memcache
So I get this error when running with dev_appserver.py: ImportError: No module named memcache
Can I use this library without modifying it?