avoid subtle interaction between importing multiprocessing and twisted

[williamstein]

It turns out that on some platforms, importing multiprocessing, then twisted, leads to an "int object is not callable" TypeError. This breaks devel/sage/sage/all.py's quit_sage function, causing a big traceback at exit. This could also cause great confusion for people writing a program that uses @parallel('multiprocessing') followed by anything involving twisted.

A simple fix is to import the relevant part of twisted before using multiprocessing in @parallel. The attached patch does this.

NOTE: The system that exhibits this is in a corporate setting, and no devs have systems where this can be replicated at present, unfortunately. So please do NOT revert this just because you don't see the problem on your laptop!

Component: misc

Author: William Stein

Reviewer: Mariah Lennox

Merged: sage-4.4.1.alpha0

Issue created by migration from https://trac.sagemath.org/ticket/8785

[williamstein]

comment:2

Attachment: trac_8785.patch.gz

[sagetrac-mariah]

comment:4

I tried it and it works!

[williamstein]

Merged: 4.4.1.alpha0

[sagetrac-mvngu]

Reviewer: Mariah Lennox

[sagetrac-mvngu]

Author: William Stein

[sagetrac-mvngu]

Changed merged from 4.4.1.alpha0 to sage-4.4.1.alpha0

[videlec]

comment:8

Would be more informative to write explicitely on which hardware/OS it failed. "corporate settings" is more than vague. Was there any upstream report? This problem might have been solved since then!