Make the custom middleware provided by Mayan to use the
MiddlewareMixin provide by Django. This make the middleware
classes behave like classes or callables. This change ensures
compatibility with Django 2.x.
Signed-off-by: Roberto Rosario <roberto.rosario.gonzalez@gmail.com>
Add COMMON_PRODUCTION_ERROR_LOG_PATH to control path of log file.
Defaults to mayan/error.log.
Add support logging request exceptions.
Signed-off-by: Roberto Rosario <roberto.rosario.gonzalez@gmail.com>