[CAPE] make link_combined_authorities more robust if CA missing

Rather than falling over spit out an error message indicating which
authority is missing to make it easier to fix

Related to #719

caps/management/commands/link_combined_authorities.py

@@ -1,28 +1,39 @@
-from caps.models import Council
 from django.core.management.base import BaseCommand, CommandError
 
 from caps.import_utils import get_council_df
-
-
-def link_combined_authorities():
-    df = get_council_df()
-
-    # limit just to those that have 'combined-authority'
-    df = df[~df["combined-authority"].isna()]
-
-    # iterate and link
-    for _, row in df.iterrows():
-        council = Council.objects.get(authority_code=row["local-authority-code"])
-        combined_authority = Council.objects.get(
-            authority_code=row["combined-authority"]
-        )
-        council.combined_authority = combined_authority
-        council.save()
+from caps.models import Council
 
 
 class Command(BaseCommand):
     help = "Adds authority codes to the csv of plans"
 
+    def link_combined_authorities(self):
+        df = get_council_df()
+
+        # limit just to those that have 'combined-authority'
+        df = df[~df["combined-authority"].isna()]
+
+        # iterate and link
+        for _, row in df.iterrows():
+            try:
+                council = Council.objects.get(
+                    authority_code=row["local-authority-code"]
+                )
+            except Council.DoesNotExist:
+                self.stderr.write(f"Can't find council {row['nice-name']}")
+            try:
+                combined_authority = Council.objects.get(
+                    authority_code=row["combined-authority"]
+                )
+            except Council.DoesNotExist:
+                self.stderr.write(
+                    f"Can't find combined authority {row['combined-authority']} for {row['nice-name']}"
+                )
+                continue
+
+            council.combined_authority = combined_authority
+            council.save()
+
     def handle(self, *args, **options):
         print("linking combined authorities")
-        link_combined_authorities()
+        self.link_combined_authorities()