for python 3.6, universal_newlines=, not text=, must be used in run()

[dimpase]

after #30740, text=True is still there, in the call to run(), and also not supported by Python 3.6.
Cf.
https://docs.python.org/3/library/subprocess.html

Changed in version 3.7: Added the text parameter, 
as a more understandable alias of universal_newlines. 
Added the capture_output parameter.

as reported on sage-release

CC: @mkoeppe @vbraun

Component: python3

Author: Dima Pasechnik

Branch/Commit: 9307ef2

Reviewer: Clemens Heuberger

Issue created by migration from https://trac.sagemath.org/ticket/30758

[dimpase]

Branch: u/dimpase/python3/no_text_in_run_for_py36

[dimpase]

Commit: 9307ef2

[dimpase]

New commits:

9307ef2

do not use the python3.7+ text= in run()

[dimpase]

Author: Dima Pasechnik

[cheuberg]

Reviewer: Clemens Heuberger

[cheuberg]

comment:2

This solves the problem on my machine, make ptestlong passes without errors.

The python3 documentation states that "The universal_newlines argument is equivalent to text and is provided for backwards compatibility." so I do not think we can introduce any new problems here. I therefore set the ticket to postive.

[mkoeppe]

comment:3

Thanks for fixing and testing this!

[vbraun]

Changed branch from u/dimpase/python3/no_text_in_run_for_py36 to 9307ef2