- update to modern python on sle15

* Small docstring fixes for release by @murrayrm in #832
- Update to version 0.9.1
- Update to version 0.8.4
* Improved default time vector for time response
* New use_legacy_defaults function to allow compatibility
* Allow creation of non-proper transfer functions
(bnavigator, rlegnain)
* Added ability to set arrow head length and width option
* Added ability to 'prewarp' the conversion of continuous to
* Added rlocus capability for discrete-time systems
* Updated pzmap grid to be compatible with matplotlib updates
* Implement loadable string representation (repr) for tf, ss,
* Fixed margin computation for discrete time systems
* Fixed InterconnectedSystem naming bugs, improved
* Fixed LinearIOSystem output bug in output function
* Fixed bug in forced_response that overrode squeeze
* Use rad/sec for Bode plot in MATLAB bode (was erroneously
* Removed deprecated scipy calls and updated to latest numpy
* Updated unit tests + switch to pytest (bnavigator,
* Return type for eigenvalues in lqe changed to 1D array
- Skip a test family on Leap because of segfaults in numpy
- moved Pillow requirement to matplotlib package
- add pr430-numpy119delete.patch to fix test failures with new numpy
- remove ppc workaround
and matrix type during tests gh#python-control/python-control#423
- skip mixsyn test on PowerPC boo#1172555
duplicated array test
- remove python-devel from BuildRequires