----------------
Bugs:
- Fix issue on Python 2 where an exception was not cleared when using
the pipe operator and was thus accessible through `sys.exc_info()`.
- The "exists" expression no longer leaks error information.
- Escape '$$' into '$' in both content and string expressions.
- Fix use of macro definition inside translation block.
Improvements:
- Allow unquoted attribute values.
- Wrap attribute error thrown when trying to use a non-macro as a
macro as a `RenderError` to get proper error output.
- Throw a parse error if '--' (double hyphen) appears in an XML
comment.
- The `i18n:target` attribute now overrides a default
`target_language` variable and is passed to the translation
function.
- Include filename in the on-disk cache module name. Previously,
only the SHA digest in hex representation would be used, making
it difficult to see where the module came from. This fixes issue
132.
- Add support for non-ascii attribute names.
[sank]
Compatibility:
- Drop support for Python 2.6, 3.1, and 3.2.