make flux Python commands more resilient to changes in PYTHONPATH #7823

Job	Run time
python linting	51s
python linting	51s
spelling	6s
spelling	6s
validate commits	10s
validate commits	10s
Generate build matrix	9s
Generate build matrix	9s
bookworm	23m 11s
bookworm	23m 11s
bookworm - 32 bit	23m 55s
bookworm - 32 bit	23m 55s
bookworm - gcc-12,content-s3,distcheck	14m 21s
bookworm - gcc-12,content-s3,distcheck	27m 57s
bookworm - py3.11,clang-15	24m 17s
bookworm - py3.11,clang-15	24m 17s
coverage	36m 55s
coverage	36m 55s
jammy - test-install	9m 50s
jammy - test-install	9m 50s
bookworm - test-install	9m 59s
bookworm - test-install	9m 59s
focal - py3.8	12m 49s
focal - py3.8	12m 49s
el8	29m 42s
el8	29m 42s
el8 - ascii	14m 25s
el8 - ascii	14m 25s
el8 - system,coverage	6m 1s
el8 - system,coverage	6m 1s
fedora34 - gcc-11.2,py3.9	13m 19s
fedora34 - gcc-11.2,py3.9	13m 19s
fedora38 - gcc-13.1,py3.11	28m 58s
fedora38 - gcc-13.1,py3.11	28m 58s
inception	24m 31s
inception	24m 31s
flux-pam check	4m 20s
flux-pam check	4m 20s
flux-accounting check	4m 8s
flux-accounting check	4m 8s
flux-sched check	5m 43s
flux-sched check	5m 43s
flux-pmix check	21m 12s
flux-pmix check	21m 12s
Generate docker manifest	0s
Generate docker manifest	1s
	10h 31m 21s

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