replace run_cmd with run_shell_cmd in custom easyblock for Python (python.py)

[bartoldeman]

(created using eb --new-pr)

[branfosj]

Test report by @branfosj

Overview of tested easyconfigs (in order)

• SUCCESS Python-2.7.18-GCCcore-10.3.0-bare.eb
• SUCCESS Python-2.7.18-GCCcore-11.2.0-bare.eb
• SUCCESS Python-2.7.18-GCCcore-11.2.0.eb
• SUCCESS Python-2.7.18-GCCcore-11.3.0-bare.eb
• SUCCESS Python-2.7.18-GCCcore-12.3.0.eb
• SUCCESS Python-3.10.4-GCCcore-11.3.0-bare.eb
• SUCCESS Python-3.10.4-GCCcore-11.3.0.eb
• SUCCESS Python-3.10.8-GCCcore-12.2.0-bare.eb
• SUCCESS Python-3.10.8-GCCcore-12.2.0.eb
• SUCCESS Python-3.11.2-GCCcore-12.2.0-bare.eb
• SUCCESS Python-3.11.3-GCCcore-12.3.0.eb
• SUCCESS Python-3.11.5-GCCcore-13.2.0.eb
• SUCCESS Python-3.9.5-GCCcore-10.3.0-bare.eb
• SUCCESS Python-3.9.5-GCCcore-10.3.0.eb
• SUCCESS Python-3.9.6-GCCcore-11.2.0-bare.eb
• SUCCESS Python-3.9.6-GCCcore-11.2.0.eb
• SUCCESS Tkinter-2.7.18-GCCcore-10.2.0.eb
• SUCCESS Tkinter-2.7.18-GCCcore-11.2.0.eb
• SUCCESS Tkinter-3.10.4-GCCcore-11.3.0.eb
• SUCCESS Tkinter-3.10.8-GCCcore-12.2.0.eb
• SUCCESS Tkinter-3.11.3-GCCcore-12.3.0.eb
• SUCCESS Tkinter-3.9.6-GCCcore-11.2.0.eb
• SUCCESS Tk-8.6.13-GCCcore-13.2.0.eb
• SUCCESS Tkinter-3.11.5-GCCcore-13.2.0.eb

Build succeeded for 24 out of 24 (23 easyconfigs in total)
bear-pg0105u03b - Linux RHEL 8.6, x86_64, Intel(R) Xeon(R) Platinum 8360Y CPU @ 2.40GHz (icelake), Python 3.6.8
See https://gist.github.com/branfosj/290da56a06b612c21660c3ea79a8ec39 for a full test report.

[branfosj]

Going in, thanks @bartoldeman!