v3.1.0 - error on multiple configs

[jethror1]

• additional check for only one config file of a given version found, this ensures we unambiguously can select the correct file to use in the case of errors
• addresses https://github.com/eastgenomics/egg5_dias_CEN_config/issues/53

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This change is 

[pep8speaks]

Hello @jethror1! Thanks for opening this PR. We checked the lines you've touched for PEP 8 issues, and found:

• In the file resources/home/dnanexus/dias_batch/tests/test_dx_requests.py:

Line 277:5: E303 too many blank lines (2) Line 290:27: E203 whitespace before ':' Line 298:27: E203 whitespace before ':' Line 306:27: E203 whitespace before ':' Line 326:54: W605 invalid escape sequence '(' Line 326:64: W605 invalid escape sequence ')' Line 327:27: W605 invalid escape sequence '(' Line 327:37: W605 invalid escape sequence ')'

[jethror1]

Test job that is a clone of the one in the linked issue: https://platform.dnanexus.com/panx/projects/GfBY2K84bkgxbx7y3z6q83k9/monitor/job/GfZPB904bkgvQf34242jvv3k