One of the more annoying things just after installing Eclipse, PyDev and Google AppEngine SDK is an error about memcache unresolved import.
I did some searching and found this. Unfortunately it did not help in my case.
What fixed it for me was going to Preferences -> PyDev -> Interpreter – Python -> Libraries, clicking New Folder button and adding the google_appengine folder (the one where you have
After clicking OK and closing Preferences I had to close the Eclipse and open it again.
PS: I had to leave the force build entry from Stack Overflow tip in my settings as well. When I removed it the error appeared again.