Now that bootstrap script automatically installs the latest published version, it's no longer necessary to track the _current_ bootstrap version with a bookmark.

Use RawConfigParser instead of SafeConfigParser in PyPIConfig class. Interpolated values are no longer supported. Since backward compatibility could not be retained in either case, prefer the simpler, more direct format. Ref #442.

Use SafeConfigParser in PyPIConfig file. Allows percent signs to be specified using two percent signs. Fixes #442.

Add another test capturing violated expectation that SandboxViolation would be raised in a sandbox/hidden_setuptools context. Ref #440.

Refine test to not make additional references to exceptions in setuptools.sandbox, but instead create a bespoke unpickleable exception. Ref #440.