Skip uninstallable tags in QPY backwards compatibility tests

[jakelishman]

Summary

When a tag has been made, but the package has not yet landed on PyPI, the QPY job fails in the environment-building step. This is not actually a failure of the QPY backwards-compatibility guarantees, and it isn't the job of the QPY tests to detect a bad tag anyway.

Details and comments

Since this commit is an acknowledgement that not every tag might be a valid version, and my editor was complaining about the safety of the various script calls, I made the variable expansion safe against word splitting, just in case.

[qiskit-bot]

One or more of the following people are relevant to this code:

• @Qiskit/terra-core
• @mtreinish
• @nkanazawa1989

[coveralls]

Pull Request Test Coverage Report for Build 10962477326

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 13 unchanged lines in 4 files lost coverage.
• Overall coverage decreased (-0.01%) to 88.781%

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Files with Coverage Reduction	New Missed Lines	%
crates/qasm2/src/expr.rs	1	94.02%
crates/accelerate/src/two_qubit_decompose.rs	1	91.45%
crates/qasm2/src/lex.rs	5	92.23%
crates/qasm2/src/parse.rs	6	97.15%

Totals
Change from base Build 10960489019:	-0.01%
Covered Lines:	73479
Relevant Lines:	82764

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💛 - Coveralls