m2m_changed signal does not fire in django admin when using inlines

[Iman Mirzadeh]

in django admin if we use inline(tabular or stacked) for many to many field, after editing it on admin the m2m_changed signal does not fire !!
if we use normal fields it works

#models.py
class TestModel(models.Model):
    name = models.CharField(max_length = 100)
    events = models.ManyToManyField(Event,related_name="testmodels")

#admin.py
@admin.register(TestModel)
class TestModelAdmin(admin.ModelAdmin):
    list_display = ("__unicode__","name")
    inlines = [EventInline,]
    exclude = ('events',)

but when I change it to

@admin.register(TestModel)
class TestModelAdmin(admin.ModelAdmin):
    list_display = ("__unicode__","name")

it works fine and signal triggered !
actually I found that the main problem is :

    exclude = ('events',)

But this is a bug because when we add something inline in admin using m2m relationship,the signal does not fire!!

[Tim Graham]

This is a limitation as documented in 9d104a21e20f9c5ec41d19fd919d0e808aa13dba.