Use builtin_str for all auto-set header values.
Add clarification to MissingSchema error
use .format()
update internal dependencies
urllib3/chardet note in release for v2.0.1
Merge pull request #1693 from kevinburke/schema-message

Add clarification to MissingSchema error
Merge pull request #1689 from Lukasa/unicode

Use builtin_str for all auto-set header values.