python - Graceful error handling and logging in Jinja extension -

i'm developing jinja extension performs few potentially harmful operations, on failure raise exception holds information on went wrong.

when occurs, of course exception prevent jinja completing render process , return none rather render result. problem mitigated using try/catch statement , returning empty string or whatever suitable.

however, throws away exception , debugging info, rather pass on error log. system responsible setting jinja environment has it's own logging service, prefer keep decoupled extension. aware though, jinja has undefined class have used intercept access of undefined variables in project.

is there way raise special type of exception (undefinedexception did not work), or tell jinja environment log warning, when error occurs in extension, while still allowing continue execution?

what have in mind along lines of example:

def _render(*args, **kwrags):     # ...     try:         self.potentially_harmful_operation()     except exception e:         self.environment.warning(e)         return markup("")     # ...     return markup('<img src"{}">'.format(img_path)) 

so, clarify, wrote in comment below:

fundamentally guess question boils down "how can make jinja produce warning, e.g. missing variables".

for interested, managed solve implementing own undefined class (largely inspired make_logging_undefined , supplying environment using undefined keyword. depending on needs, default make_logging_undefined might suffice.

once that's in place, trick emit warning in environment. done instantiating environment's undefined , executing 1 of magic methods (e.g. __str__). hooking on example code above, accomplished this:

def _render(*args, **kwrags):     # ...     try:         self.potentially_harmful_operation()     except exception e:         str(self.environment.undefined(e))         return markup("")     # ...     return markup('<img src"{}">'.format(img_path))