Provide better error handling when parsing a jinja template with possible moustach errors

[fsuits]

Issue description / feature objectives

If moustaches appear in markdown that is being used by a jinja template, jinja can give an opaque error such as jinja2.exceptions.TemplateSyntaxError: expected token 'end of print statement', got ':'

If possible an error handler should report a clear message if such parsing errors occur.