Implement method gap of class PermutationGroupElement properly. #27234
Description
This is a follow up ticket of #26750. In that ticket the method has been implemented as synonym of _gap_, since at that time libgap produced an error for large permutations.
┌────────────────────────────────────────────────────────────────────┐
│ SageMath version 8.5, Release Date: 2018-12-22 │
│ Using Python 2.7.15. Type "help()" for help. │
└────────────────────────────────────────────────────────────────────┘
sage: P = PGU(8,2)
sage: p1, p2 = P.gens()
sage: libgap(p1)
python2: libgap.c:184: libgap_get_input: Assertion `strlen(libGAP_stdin_buffer) < length' failed.
Traceback (most recent call last):
...
ValueError: libGAP: Aborted
This error has been fixed in 8.6.beta0. Therefore, we may have gap using libgap, right now!
Component: group theory
Keywords: libgap, permutation
Author: Sebastian Oehms
Branch/Commit: 0e444c5
Reviewer: Travis Scrimshaw
Issue created by migration from https://trac.sagemath.org/ticket/27234