Bump chameleon from 2.22 to 3.9.1

[dependabot-preview]

Bumps chameleon from 2.22 to 3.9.1.

Changelog

Sourced from chameleon's changelog.

3.9.1 (2021-05-14)

• Avoid various traceback reference cycles.

3.9.0 (2021-02-26)

• Removed compatibility code for unsupported Python versions
• Dropped support for obsolete Python 3.4
• Fixed namespace handling when redefining a variable in the same tal:define (#237)
• Fixed failure computing a template's digest if template.filename is None (#254)

3.8.1 (2020-07-06)

• Added code optimization to reduce sequential appends of static text.
• The default symbol in dynamic attributes is now symbolic. Previously, it was assigned the string value of the default attribute text. A similar change has been made for switch/case expressions.
• The built-in attrs dictionary of static element attributes now correctly works with tal:define, etc.
• Fix slice code generation compatibility issue on Python 3.9.

3.8.0 (2020-06-25)

• Expose default marker as importable symbol chameleon.tales.DEFAULT_MARKER.
• Removed legacy flag literal_false. To get a similar behavior, use boolean_attributes.

3.7.4 (2020-06-17)

• Fix brown-bag release.

3.7.3 (2020-06-17)

• Fix regression introduced in 3.6.2 where the default marker would incorrectly change its value between templates, causing issues in software which depends on the value being treated as a global object.

3.7.2 (2020-05-31)

• Allow setting a custom value representation function, allowing custom formatting of variables during exception formatting.

3.7.1 (2020-05-10)

• Fix compatiblity issue with Python 3.9.

3.7.0 (2020-03-26)

... (truncated)

Commits

• 7c0c3fe Preparing release
• 5278083 Merge pull request #344 from cjwatson/traceback-reference-cycle
• 48716ef Avoid various traceback reference cycles
• e7034bd Merge pull request #343 from felixonmars/patch-1
• 800df45 Correct a typo in test_templates.py
• 407402f - vb [ci skip]
• b0a3a92 - prepare release 3.9.0
• a3e495c Merge pull request #340 from malthe/dataflake/issue_254
• b94fa46 Merge pull request #341 from malthe/dataflake/cleanup
• d835cd4 - Removed compatibility code for unsupported Python versions
• Additional commits viewable in compare view

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