Fix IP is none error in doctests

[tobiasdiez]

The sage doctester, when invoked from plain Python, errors out because IPython is not initialized:

./sage -python -c 'import sage.all; import sage.doctest.control; sage.doctest.control.run_doctests(sage)'
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/Users/mkoeppe/s/sage/sage-rebasing/worktree-algebraic-2018-spring/local/lib/python3.7/site-packages/sage/doctest/control.py", line 1305, in run_doctests
    old_color = IP.colors
AttributeError: 'NoneType' object has no attribute 'colors'

This is fixed by adding a check for none.

CC: @mkoeppe @dimpase

Component: doctest framework

Author: Tobias Diez

Branch/Commit: 042825b

Reviewer: Matthias Koeppe

Issue created by migration from https://trac.sagemath.org/ticket/30935

[mkoeppe]

comment:2

Could you expand the ticket description please? How does one provoke this error?

[tobiasdiez]

comment:3

The error happened while running

import sage.all
import sage.doctest.control
sage.doctest.control.run_doctests(sage)

via the VS Code "Run Python file in terminal". (I know that is a somewhat none-standard form to run the doctests.) Stack trace:

Traceback (most recent call last):
  File "/mnt/d/Programming/Projects/sage/src/test_docs.py", line 3, in <module>
    sage.doctest.control.run_doctests(sage)
  File "/mnt/d/Programming/Projects/sage/src/sage/doctest/control.py", line 1305, in run_doctests
    old_color = IP.colors
AttributeError: 'NoneType' object has no attribute 'colors'

[mkoeppe]

Reviewer: Matthias Koeppe

[tobiasdiez]

comment:6

Thanks!

[vbraun]

Changed branch from public/doctest/ipythonnot to 042825b