Django management command to trace / list all signals. My fork is just a few cleanups where CommandError wasn't referenced, etc.

signals.py

# coding:utf-8

import gc
import inspect
import weakref

from django.core.management.base import BaseCommand, CommandError
from django.dispatch import Signal
from django.dispatch.weakref_backports import WeakMethod
from optparse import make_option


REF_TYPES = (weakref.ReferenceType, WeakMethod, WeakMethod)

FORMATS = {
    'vim': '{path}:{line}:{name}',
    'human': '{name} in line {line} of {path}',
}


class Command(BaseCommand):
    help = 'Show all signals receivers'
    option_list = BaseCommand.option_list + (
        make_option(
            '--format',
            dest='line_format',
            default='human',
            choices=FORMATS.keys(),
            help='Line format (available choices: {0})'.format(', '.join(FORMATS)),
        ),
    )

    def handle(self, *args, **options):
        line_format = options['line_format']
        if line_format not in FORMATS:
            raise CommandError('format must be on of {0}, not {1}'.format(line_format, FORMATS.keys()))
        msg = FORMATS[line_format]
        signals = [obj for obj in gc.get_objects() if isinstance(obj, Signal)]
        for signal in signals:
            for receiver in signal.receivers:
                _, receiver = receiver
                # django.contrib.contenttypes.generic.GenericForeignKey.instance_pre_init is not weakref
                if isinstance(receiver, REF_TYPES):
                    receiver = receiver()
                print msg.format(
                    name=receiver.func_name,
                    line=inspect.getsourcelines(receiver)[1],
                    path=inspect.getsourcefile(receiver)
                )

Tested with Django 1.8