prompt: We are currently solving the following issue within our repository. Here is the issue text:
  --- BEGIN ISSUE ---
  Change Mezzanine Form to Disallow Username Changes
  **Describe the feature you'd like and what it will do**
  The internal mezzanine form for the admin account should be altered to no longer allow username changes if possible, since doing so breaks the resource. 
  
  
  **Why is this feature important?**
  This will be policy moving forward, that usernames cannot be changed. 
  I will work with Scott to see if this change is feasible. 
  
  
  --- END ISSUE ---
  
  Below are some code segments, each from a relevant file. One or more of these files may contain bugs.
  --- BEGIN FILES ---
  Path: `hs_core/admin.py`
  Content:
  ```
  1 from django import forms
  2 from django.contrib.auth.admin import UserAdmin
  3 from django.contrib.auth.forms import UserCreationForm
  4 from django.contrib.gis import admin
  5 from django.contrib.contenttypes.admin import GenericTabularInline
  6 from django.utils.translation import ugettext_lazy as _
  7 
  8 from .models import *
  9 
  10 
  11 class UserCreationFormExtended(UserCreationForm):
  12     def __init__(self, *args, **kwargs):
  13         super(UserCreationFormExtended, self).__init__(*args, **kwargs)
  14         self.fields['email'] = forms.EmailField(label=_("E-mail"), max_length=75)
  15 
  16 UserAdmin.add_form = UserCreationFormExtended
  17 UserAdmin.add_fieldsets = (
  18     (None, {
  19         'classes': ('wide',),
  20         'fields': ('email', 'username', 'password1', 'password2',)
  21     }),
  22 )
  23 UserAdmin.list_display = [
  24     'username', 'email', 'first_name', 'last_name', 'is_staff',
  25     'is_active', 'date_joined', 'last_login'
  26 ]
  27 
  28 class InlineResourceFiles(GenericTabularInline):
  29     model = ResourceFile
  30 
  31 admin.site.unregister(User)
  32 admin.site.register(User, UserAdmin)
  33 admin.site.unregister(GenericResource)
  34
  ```
  --- END FILES ---
  
  Please first localize the bug based on the issue statement, and then generate a patch according to the `git diff` format fenced by three backticks.
  
  Here is an example:
  
  ```diff
  diff --git a/examples/server_async.py b/examples/server_async.py
  --- a/examples/server_async.py
  +++ b/examples/server_async.py
  @@ -313,4 +313,4 @@
   
   
   if __name__ == "__main__":
  -    asyncio.run(run_async_server("."), debug=True)
  +    asyncio.run(run_async_server(), debug=True)
  diff --git a/examples/server_sync.py b/examples/server_sync.py
  --- a/examples/server_sync.py
  +++ b/examples/server_sync.py
  @@ -313,5 +313,5 @@
   
   
   if __name__ == "__main__":
  -    server = run_sync_server(".")
  +    server = run_sync_server()
       server.shutdown()
  
  ```
  
golden_diff: diff --git a/hs_core/admin.py b/hs_core/admin.py
  --- a/hs_core/admin.py
  +++ b/hs_core/admin.py
  @@ -14,6 +14,7 @@
           self.fields['email'] = forms.EmailField(label=_("E-mail"), max_length=75)
   
   UserAdmin.add_form = UserCreationFormExtended
  +UserAdmin.readonly_fields = ('username',)
   UserAdmin.add_fieldsets = (
       (None, {
           'classes': ('wide',),
  
verification_info: {"golden_diff": "diff --git a/hs_core/admin.py b/hs_core/admin.py\n--- a/hs_core/admin.py\n+++ b/hs_core/admin.py\n@@ -14,6 +14,7 @@\n         self.fields['email'] = forms.EmailField(label=_(\"E-mail\"), max_length=75)\n \n UserAdmin.add_form = UserCreationFormExtended\n+UserAdmin.readonly_fields = ('username',)\n UserAdmin.add_fieldsets = (\n     (None, {\n         'classes': ('wide',),\n", "issue": "Change Mezzanine Form to Disallow Username Changes\n**Describe the feature you'd like and what it will do**\r\nThe internal mezzanine form for the admin account should be altered to no longer allow username changes if possible, since doing so breaks the resource. \r\n\r\n\r\n**Why is this feature important?**\r\nThis will be policy moving forward, that usernames cannot be changed. \r\nI will work with Scott to see if this change is feasible. \r\n\n", "before_files": [{"content": "from django import forms\nfrom django.contrib.auth.admin import UserAdmin\nfrom django.contrib.auth.forms import UserCreationForm\nfrom django.contrib.gis import admin\nfrom django.contrib.contenttypes.admin import GenericTabularInline\nfrom django.utils.translation import ugettext_lazy as _\n\nfrom .models import *\n\n\nclass UserCreationFormExtended(UserCreationForm):\n    def __init__(self, *args, **kwargs):\n        super(UserCreationFormExtended, self).__init__(*args, **kwargs)\n        self.fields['email'] = forms.EmailField(label=_(\"E-mail\"), max_length=75)\n\nUserAdmin.add_form = UserCreationFormExtended\nUserAdmin.add_fieldsets = (\n    (None, {\n        'classes': ('wide',),\n        'fields': ('email', 'username', 'password1', 'password2',)\n    }),\n)\nUserAdmin.list_display = [\n    'username', 'email', 'first_name', 'last_name', 'is_staff',\n    'is_active', 'date_joined', 'last_login'\n]\n\nclass InlineResourceFiles(GenericTabularInline):\n    model = ResourceFile\n\nadmin.site.unregister(User)\nadmin.site.register(User, UserAdmin)\nadmin.site.unregister(GenericResource)\n", "path": "hs_core/admin.py"}], "after_files": [{"content": "from django import forms\nfrom django.contrib.auth.admin import UserAdmin\nfrom django.contrib.auth.forms import UserCreationForm\nfrom django.contrib.gis import admin\nfrom django.contrib.contenttypes.admin import GenericTabularInline\nfrom django.utils.translation import ugettext_lazy as _\n\nfrom .models import *\n\n\nclass UserCreationFormExtended(UserCreationForm):\n    def __init__(self, *args, **kwargs):\n        super(UserCreationFormExtended, self).__init__(*args, **kwargs)\n        self.fields['email'] = forms.EmailField(label=_(\"E-mail\"), max_length=75)\n\nUserAdmin.add_form = UserCreationFormExtended\nUserAdmin.readonly_fields = ('username',)\nUserAdmin.add_fieldsets = (\n    (None, {\n        'classes': ('wide',),\n        'fields': ('email', 'username', 'password1', 'password2',)\n    }),\n)\nUserAdmin.list_display = [\n    'username', 'email', 'first_name', 'last_name', 'is_staff',\n    'is_active', 'date_joined', 'last_login'\n]\n\nclass InlineResourceFiles(GenericTabularInline):\n    model = ResourceFile\n\nadmin.site.unregister(User)\nadmin.site.register(User, UserAdmin)\nadmin.site.unregister(GenericResource)\n", "path": "hs_core/admin.py"}]}