forms.py
#为原始form添加BootstrapMixin
from bootstrap.forms import BootstrapMixin

class BsAuthenticationForm(AuthenticationForm, BootstrapMixin):
 def __init__(self, *args, **kw):
  super(BsAuthenticationForm, self).__init__(*args, **kw)
  self.__bootstrap__()
 
urls.py
#重写urls，指定使用的form
from django.conf.urls.defaults import *
from userena import views as userena_views
from profiles.forms import BsSignupForm, BsAuthenticationForm

urlpatterns = patterns('',
 url(r'^signup/$', userena_views.signup,
  {'signup_form': BsSignupForm}, name='userena_signup'),
 url(r'^signin/$', userena_views.signin,
  {'auth_form': BsAuthenticationForm}, name='userena_signin'),
 (r'^', include('userena.urls')),
)

USERNAME_RE = r'^\S+$'
attrs_dict = {'class': 'required'}

class BsSignupForm(SignupForm, BootstrapMixin):
 username = forms.RegexField(regex=USERNAME_RE,
        max_length=30,
        widget=forms.TextInput(attrs=attrs_dict),
        label=_("Username"),
        error_messages={'invalid': _('Username must contain only letters, numbers, dots and underscores.')})

 def __init__(self, *args, **kw):
  super(BsSignupForm, self).__init__(*args, **kw)
  self.__bootstrap__()