Add --check to user import

Signed-off-by: Michal Čihař <michal@cihar.com>

docs/admin/management.rst

@@ -159,13 +159,16 @@ importuserdata <file.json>
 
 Imports userdata from file created by :djadmin:`dumpuserdata`
 
-importusers <file.json>
------------------------
+importusers --checck <file.json>
+--------------------------------
 
 .. django-admin:: importusers
 
 Imports users from JSON dump of Django auth_users database.
 
+With ``--check`` it will just check whether given file can be imported and
+report possible conflicts on usernames or emails.
+
 You can dump users from existing Django installation using:
 
 .. code-block:: sh

weblate/accounts/management/commands/importusers.py

@@ -20,12 +20,20 @@
 
 from django.core.management.base import BaseCommand, CommandError
 from django.contrib.auth.models import User
+from optparse import make_option
 import json
 
 
 class Command(BaseCommand):
     help = 'imports users from JSON dump of database'
     args = '<json-file>'
+    option_list = BaseCommand.option_list + (
+        make_option(
+            '--check',
+            action='store_true',
+            help='Only check import, do not actually create users'
+        ),
+    )
 
     def handle(self, *args, **options):
         '''
@@ -41,14 +49,23 @@ class Command(BaseCommand):
             if 'fields' in line:
                 line = line['fields']
 
+            if 'is_active' in line and not line['is_active']:
+                continue
+
+            if not line['email'] or not line['username']:
+                self.stderr.write(
+                    'Skipping {}, has blank username or email'.format(line)
+                )
+                continue
+
             if User.objects.filter(username=line['username']).exists():
-                self.stdout.write(
+                self.stderr.write(
                     'Skipping {}, username exists'.format(line['username'])
                 )
                 continue
 
             if User.objects.filter(email=line['email']).exists():
-                self.stdout.write(
+                self.stderr.write(
                     'Skipping {}, email exists'.format(line['email'])
                 )
                 continue
@@ -61,6 +78,7 @@ class Command(BaseCommand):
             else:
                 full_name = line['first_name']
 
+            if not options['check']:
                 User.objects.create(
                     username=line['username'],
                     first_name=full_name,