As it has mentioned in an earlier posting sage-4.7.1 will only start if it has
been emerged with the "testsuite" useflag. I believe this was caused by the
inclusion of the following ticket:
What happens, if I am not mistaken, is that sage is capable of introspect its
own code to find information about the syntax of any commands. To do this it
needs to have the code. That's not a problem with python file as it is code
already. But sage can also look at its cython source files. The above ticket
changed the behavior of the introspection of cython files. Traditionally we
don't ship the cython source files unless the testsuite flag is enabled. The
big worry in my opinion is sage is now checking its source code including cython
files on start up. That can't be good for sage start up time.
I'll try to get in touch with one of the ticket author to see if it is the
desired behavior or if something needs to be fixed.