Check for missing part thumbnails when the server first runs

InvenTree/part/apps.py

@@ -1,7 +1,36 @@
 from __future__ import unicode_literals
 
+import os
+
+from django.db.utils import OperationalError, ProgrammingError
 from django.apps import AppConfig
+from django.conf import settings
 
 
 class PartConfig(AppConfig):
     name = 'part'
+
+    def ready(self):
+        """
+        This function is called whenever the Part app is loaded.
+        """
+
+        self.generate_part_thumbnails()
+
+    def generate_part_thumbnails(self):
+        from .models import Part
+
+        print("Checking Part image thumbnails")
+
+        try:
+            for part in Part.objects.all():
+                if part.image:
+                    url = part.image.thumbnail.name
+                    #if url.startswith('/'):
+                    #    url = url[1:]
+                    loc = os.path.join(settings.MEDIA_ROOT, url)
+                    if not os.path.exists(loc):
+                        print("InvenTree: Generating thumbnail for Part '{p}'".format(p=part.name))
+                        part.image.render_variations(replace=False)
+        except (OperationalError, ProgrammingError):
+            print("Could not generate Part thumbnails")