Make sure image files has a name associated.

The generate image command will run into issues if the ImageSpecField does not
have any image file source associated wit hti. Like a Optional image field. So
we can not generate the images for that. So this should check to make sure that
it has one.

imagekit/management/commands/generateimages.py

@@ -1,6 +1,7 @@
 from django.core.management.base import BaseCommand
 import re
 from ...registry import generator_registry, cachefile_registry
+from ...exceptions import MissingSource
 
 
 class Command(BaseCommand):
@@ -22,14 +23,15 @@ well as "a:b" and "a:b:c".""")
 
         for generator_id in generators:
             self.stdout.write('Validating generator: %s\n' % generator_id)
-            for file in cachefile_registry.get(generator_id):
-                self.stdout.write('  %s\n' % file)
-                try:
-                    # TODO: Allow other validation actions through command option
-                    file.generate()
-                except Exception as err:
-                    # TODO: How should we handle failures? Don't want to error, but should call it out more than this.
-                    self.stdout.write('    FAILED: %s\n' % err)
+            for image_file in cachefile_registry.get(generator_id):
+                if image_file.name:
+                    self.stdout.write('  %s\n' % image_file.name)
+                    try:
+                        image_file.generate()
+                    except MissingSource as err:
+                        self.stdout.write('\t No source associated with\n')
+                    except Exception as err:
+                        self.stdout.write('\tFailed %s\n' % (err))
 
     def compile_patterns(self, generator_ids):
         return [self.compile_pattern(id) for id in generator_ids]