Remove stack traces from intentional 4xx exception logging

ForbiddenError403, BadRequestError400, and MultiPartParserError are
intentional error responses, not unexpected failures. Logging them with
exc_info produced misleading stack traces that looked like bugs and
created noise in error tracking tools like Sentry.

Keep the WARNING messages (they have diagnostic value) but drop the
stack traces, consistent with how FormFieldMissingError already works.
SuspiciousOperationError400 and unhandled 500s retain their stack traces.

Author: davegaeddert

plain/plain/internal/handlers/exception.py

@@ -37,7 +37,6 @@ def response_for_exception(request: Request, exc: Exception) -> ResponseBase:
             "Forbidden (Permission denied): %s",
             request.path,
             extra={"status_code": response.status_code, "request": request},
-            exc_info=exc,
         )
 
     elif isinstance(exc, MultiPartParserError):
@@ -48,7 +47,6 @@ def response_for_exception(request: Request, exc: Exception) -> ResponseBase:
             "Bad request (Unable to parse request body): %s",
             request.path,
             extra={"status_code": response.status_code, "request": request},
-            exc_info=exc,
         )
 
     elif isinstance(exc, BadRequestError400):
@@ -60,7 +58,6 @@ def response_for_exception(request: Request, exc: Exception) -> ResponseBase:
             str(exc),
             request.path,
             extra={"status_code": response.status_code, "request": request},
-            exc_info=exc,
         )
     elif isinstance(exc, SuspiciousOperationError400):
         # The request logger receives events for any problematic request