SG-38306 Python2 Removal - Part 7 - various

[julien-lang]

• Cleanup six.PY2/six.PY3 conditions
• Remove useless test in Python 3
• Replace sgsix.file_types by io.IOBase
• Replace ShotgunSSLError by ssl.SSLError
• Cleanup Python-2 related comments and workarounds

PR orders

• SG-38306 Python2 Removal - Part 1 - Import order #398
• SG-38306 Python2 Removal - Part 2 - Easy ones #399
• SG-38306 Python2 Removal - Part 3 - Cleanup imports #400
• SG-38306 Python2 Removal - Part 4 - Mimetypes module #401
• SG-38306 Python2 Removal - Part 5 - Remove deprecated backported mock module #402
• SG-38306 Python2 Removal - Part 6 - Remove python2 from httplib2 module #403
• SG-38306 Python2 Removal - Part 7 - various #404
• SG-38306 Python2 Removal - Part 8 - Remove deprecated ensure_ascii parameter from SG object #405
• SG-38306 Python2 Removal - Part 9 - six module #395
• SG-38306 Remove Python 2 - Part 10 - SSL #372

[Copilot]

Pull Request Overview

This PR continues the Python 2 removal effort by cleaning up legacy Python 2/3 compatibility code, updating error handling, and modernizing imports.

• Removed six.PY2/six.PY3 branches and outdated workarounds
• Replaced sgsix.file_types with io.IOBase and ShotgunSSLError with ssl.SSLError
• Simplified tests and CI configuration to target Python 3 only

Reviewed Changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
tests/test_client.py	Removed Python 2/3 guard around json.dumps; always call without encoding
tests/test_api.py	Dropped ShotgunSSLError import, switched exception handling to ssl.SSLError
tests/base.py	Removed Python 2-specific json.dumps(..., encoding="utf-8") branch
shotgun_api3/shotgun.py	Updated imports (removed sgsix), added XML parsing in error handler, replaced sgsix.file_types with io.IOBase
azure-pipelines-templates/run-tests.yml	Updated comments to reflect Python 3 versions only
README.md	Cleaned up documentation by removing outdated Python 2/3 notes

Comments suppressed due to low confidence (2)

shotgun_api3/shotgun.py:2926

• [nitpick] The new XML parsing branch in download_attachment error handling isn’t covered by existing tests. Consider adding a unit test that simulates an S3 XML error response to verify that the <Message> extraction works as intended.

 root = xml.etree.ElementTree.fromstring("".join(body)) 

tests/test_api.py:2259

• The code now references ssl.SSLError but ssl is not imported in this file. Please add import ssl at the top of tests/test_api.py.

 mock_request.side_effect = ssl.SSLError( 

[carlos-villavicencio-adsk]

LGTM. Just a couple of nitpicky suggestions.

The base branch was changed.