docs: def wsgi(self, environ, start_response):
          """ The bottle WSGI-interface. """
          try:
              out = self._cast(self._handle(environ))
              # rfc2616 section 4.3
              if response._status_code in (100, 101, 204, 304)\
              or environ['REQUEST_METHOD'] == 'HEAD':
                  if hasattr(out, 'close'): out.close()
                  out = []
              start_response(response._status_line, response.headerlist)
              return out
          except (KeyboardInterrupt, SystemExit, MemoryError):
              raise
          except Exception:
              if not self.catchall: raise
              err = '<h1>Critical error while processing request: %s</h1>' \
                    % html_escape(environ.get('PATH_INFO', '/'))
              if DEBUG:
                  err += '<h2>Error:</h2>\n<pre>\n%s\n</pre>\n' \
                         '<h2>Traceback:</h2>\n<pre>\n%s\n</pre>\n' \
                         % (html_escape(repr(_e())), html_escape(format_exc()))
              environ['wsgi.errors'].write(err)
              headers = [('Content-Type', 'text/html; charset=UTF-8')]
              start_response('500 INTERNAL SERVER ERROR', headers, sys.exc_info())
              return [tob(err)]