When a ValidationError exception is raised, e.g.
the error message(s) of the erroneous field(s) are not processed correct by our custom error handler and Django in the later. This leads into an empty Response.content/Response.text variable or to be more precise, the error message is not forwarded to the API caller because it gets lost during the exception handling process.
Note, if the ValidationError is raised with a single message string, e.g.
then the final error message must be transformed into