PythonPlugin: replace deprecated/removed Eval with Exec #1591

Job	Run time
Upload Event Payload	3s
key4hep (/cvmfs/sw-nightlies.hsf.org/key4hep/)	29m 52s
default (LCG_101/x86_64-centos7-gcc11-opt)	24m 43s
g4units (dev3/x86_64-el9-gcc13-opt)	27m 1s
default (LCG_102/x86_64-centos9-gcc11-opt)	28m 40s
non-shared (LCG_105/x86_64-centos7-gcc11-opt)	12m 4s
default (LCG_104/x86_64-el9-gcc13-opt)	1h 9m 11s
default (LCG_105/x86_64-ubuntu2204-gcc11-opt)	1h 5m 30s
default (dev3/x86_64-el9-gcc13-opt)	41m 46s
default (dev3/x86_64-el9-clang16-opt)	42m 46s
default (dev4/x86_64-el9-gcc13-opt)	26m 6s
	6h 7m 42s

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