more specific error handling in undefined jinja variables rule

[lperson]

1. Use regex to extract variable name from exception message
2. Specific handling for ValueError and TypeError
3. Defend against endless loop

[boring-cyborg]

Congratulations on your first Pull Request and welcome to the Apache Airflow community! If you have any issues or are unsure about any anything please check our Contribution Guide (https://github.com/apache/airflow/blob/master/CONTRIBUTING.rst)
Here are some useful points:

• Pay attention to the quality of your code (flake8, pylint and type annotations). Our pre-commits will help you with that.
• In case of a new feature add useful documentation (in docstrings or in docs/ directory). Adding a new operator? Check this short guide Consider adding an example DAG that shows how users should use it.
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• Be patient and persistent. It might take some time to get a review or get the final approval from Committers.
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• Be sure to read the Airflow Coding style.
  Apache Airflow is a community-driven project and together we are making it better 🚀.
  In case of doubts contact the developers at:
  Mailing List: dev@airflow.apache.org
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[mik-laj]

Caan you add tests to avoid regression?

[RosterIn]

Suggested change

	"Error: 'NoneType' object is not iterable",
	"Error: 'NoneType' object is not iterable, "

[kaxil]

We removed this check in 1.2.0 of upgrade-check