Fix crash when z3 is missing and add transform error reporting

[david-yz-liu]

Proposed Changes

(Describe your changes here. Also describe the motivation for your changes: what problem do they solve, or how do they improve the application or codebase? If this pull request fixes an open issue, use a keyword to link this pull request to the issue.)

This pull request fixes #1117 and adds logging for when Z3Visitor and CFGVisitor fail to run. In particular, this will report a warning if the z3 option is enabled, but z3-solver was not installed.

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Type	Applies?
🚨 Breaking change (fix or feature that would cause existing functionality to change)
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[coveralls]

Pull Request Test Coverage Report for Build 12213927042

Details

• 6 of 12 (50.0%) changed or added relevant lines in 1 file are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage decreased (-0.1%) to 91.861%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
python_ta/patches/transforms.py	6	12	50.0%

Files with Coverage Reduction	New Missed Lines	%
python_ta/patches/transforms.py	1	66.67%

Totals
Change from base Build 12098022807:	-0.1%
Covered Lines:	3104
Relevant Lines:	3379

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💛 - Coveralls