[with patch] Bad error message when running a script

[was]

1. Create a script test.sage with this 1 line

solve([x==1], x)

2. Run it like so:

  $ sage test.sage
  Exception exceptions.AttributeError: "'NoneType' object has no attribute 'ExceptionPexpect'" in  ignored

3. If you put instead

print solve([x==1], x)

then everything works fine.

Clearly there is a bug there, probably with quitting the pexpect interface to maxima.

[malb]

I've attached a work-around for this bug (6116.patch). It is probably best to understand the behaviour first, but the attached patch works around it for now.

[mabshoff]

[09:58] <mabshoff> But it would still be interesting to see what causes the problem.
[09:59] <janwil> yes, it's a mystery to me right now ...
[09:59] <mabshoff> Not only to you :)
[09:59] <janwil> :)
[10:01] <mhansen_> Yeah, that worked for me.
[10:01] <mabshoff> malb's patch?
[10:02] <mhansen_> Yep.
[10:02] <mabshoff> Well, we should get it merged in 2.8.4.3 then. We can always revert it in case it causes 
[10:02] <mhansen_> I was also getting that error when I was running some of the tests with nose.   The tests would pass, but those would come up at the end.
[10:03] <mabshoff> trouble on a range of platforms.
[10:03] <mabshoff> Interesting.