Fix import pymc.testing

[bomtall]

Description

• Move import pytest to be local so it does not break import pymc.testing
• It is hard to write a test for this because the test will have pytest already

Related Issue

• [x ] Closes pymc.testing attempts to import pytest but pytest is not in pymc install requirements #7218
• Related to #

Checklist

• [x ] Checked that the pre-commit linting/style checks pass
• Included tests that prove the fix is effective or that the new feature works
• [ x] Added necessary documentation (docstrings and/or example notebooks)
• If you are a pro: each commit corresponds to a relevant logical change

Type of change

• New feature / enhancement
• [x ] Bug fix
• Documentation
• Maintenance
• Other (please specify):

---

📚 Documentation preview 📚: https://pymc--7357.org.readthedocs.build/en/7357/

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.37%. Comparing base (4f76576) to head (9bcc103).
Report is 114 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #7357   +/-   ##
=======================================
  Coverage   92.37%   92.37%           
=======================================
  Files         102      102           
  Lines       17207    17210    +3     
=======================================
+ Hits        15895    15898    +3     
  Misses       1312     1312           

Files with missing lines	Coverage Δ
pymc/testing.py	91.47% <100.00%> (+0.05%)	⬆️

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Congrats on merging your first pull request! 🎉 We here at PyMC are proud of you! 💖 Thank you so much for your contribution 🎁

[twiecki]

Thanks!