DRY'd startapp and startproject management commands.

django/core/management/commands/startapp.py

-from importlib import import_module
-
-from django.core.management.base import CommandError
 from django.core.management.templates import TemplateCommand
 
 
@@ -12,18 +9,6 @@ class Command(TemplateCommand):
     missing_args_message = "You must provide an application name."
 
     def handle(self, **options):
-        app_name, target = options.pop('name'), options.pop('directory')
-        self.validate_name(app_name, "app")
-
-        # Check that the app_name cannot be imported.
-        try:
-            import_module(app_name)
-        except ImportError:
-            pass
-        else:
-            raise CommandError(
-                "%r conflicts with the name of an existing Python module and "
-                "cannot be used as an app name. Please try another name." % app_name
-            )
-
+        app_name = options.pop('name')
+        target = options.pop('directory')
         super().handle('app', app_name, target, **options)

django/core/management/commands/startproject.py

-from importlib import import_module
-
-from django.core.management.base import CommandError
 from django.core.management.templates import TemplateCommand
 
 from ..utils import get_random_secret_key
@@ -14,19 +11,8 @@ class Command(TemplateCommand):
     missing_args_message = "You must provide a project name."
 
     def handle(self, **options):
-        project_name, target = options.pop('name'), options.pop('directory')
-        self.validate_name(project_name, "project")
-
-        # Check that the project_name cannot be imported.
-        try:
-            import_module(project_name)
-        except ImportError:
-            pass
-        else:
-            raise CommandError(
-                "%r conflicts with the name of an existing Python module and "
-                "cannot be used as a project name. Please try another name." % project_name
-            )
+        project_name = options.pop('name')
+        target = options.pop('directory')
 
         # Create a random SECRET_KEY to put it in the main settings.
         options['secret_key'] = get_random_secret_key()

django/core/management/templates.py

@@ -7,6 +7,7 @@ import shutil
 import stat
 import sys
 import tempfile
+from importlib import import_module
 from os import path
 from urllib.request import urlretrieve
 
@@ -210,14 +211,35 @@ class TemplateCommand(BaseCommand):
                            (self.app_or_project, template))
 
     def validate_name(self, name, app_or_project):
+        a_or_an = 'an' if app_or_project == 'app' else 'a'
         if name is None:
-            raise CommandError("you must provide %s %s name" % (
-                "an" if app_or_project == "app" else "a", app_or_project))
-        # If it's not a valid directory name.
+            raise CommandError('you must provide {an} {app} name'.format(
+                an=a_or_an,
+                app=app_or_project,
+            ))
+        # Check it's a valid directory name.
         if not name.isidentifier():
             raise CommandError(
-                "%r is not a valid %s name. Please make sure the name is "
-                "a valid identifier." % (name, app_or_project)
+                "'{name}' is not a valid {app} name. Please make sure the "
+                "name is a valid identifier.".format(
+                    name=name,
+                    app=app_or_project,
+                )
+            )
+        # Check it cannot be imported.
+        try:
+            import_module(name)
+        except ImportError:
+            pass
+        else:
+            raise CommandError(
+                "'{name}' conflicts with the name of an existing Python "
+                "module and cannot be used as {an} {app} name. Please try "
+                "another name.".format(
+                    name=name,
+                    an=a_or_an,
+                    app=app_or_project,
+                )
             )
 
     def download(self, url):