Our Markdown extensions and rendering logic made use of features or

implemented functions that have been deprecated in Python-Markdown 2.5

and 2.6. There were also behavioral changes since 2.4 that impacted our

WYSIWYG rendering.
The signature for makeExtension has changed, and the safe_mode

argument is scheduled for removal. To handle these changes, our

makeExtension functions now accept variable and keyword arguments,

which will work across all versions. To replace the safe_mode

argument, we now have a new EscapeHTMLExtension, which makes use of

Python-Markdown's recommended way of enabling escape mode (with some

small changes to prevent problems when using both the extension and

safe_mode in code that still needs to be migrated).
The WYSIWYG extension was seeing regressions in newline handling. The

extension overrides Python-Markdown's postprocessor for replacing

internal HTML placeholder markers with stashed HTML (needed by

extensions and certain Markdown directives) and attempts to prevent

trailing newlines from being injected. The implementation of

Python-Markdown's version changed, breaking the method we used to

override the behavior. We now have a re-implementation of this processor

that does an even better job of working around the newline issues, and

is actually faster than the original version.
Markdown.ESCAPE_CHARS was also no longer available. It's defined only

when an instance is created, which is a fairly heavy-weight operation

(for these purposes). Since the list has not changed since it was

introduced, it should be safe for us to define this ourselves.
2.7 will also need to now specify the full module path for all

extensions, including Python-Markdown's built-in extensions. Djblets

only specifies extension names in the tests, so this is a simple fix.
With these changes, clients will be able to use any version of Python

Markdown from 2.4 through 2.7, and likely future versions as well.

Unit tests ran against Python-Markdown 2.4 (our currently supported

version) and 2.6.
Tested with my real-world and crazy Markdown tests on Review Board with

both versions of Python-Markdown.