Add gene length to error message

This matches the equivalent error message in Auspice.¹

¹ https://github.com/nextstrain/auspice/blob/22124f8eacec2c46f39806aa95472581f65fc25a/src/util/entropyCreateStateFromJsons.ts#L315

Author: victorlin

augur/io/sequences.py

@@ -252,7 +252,7 @@ def validate_features(features):
         # Error if feature length is not a multiple of 3.
         length = len(feat.location)
         if length % 3:
-            yield f"Gene length of {feature_name!r} is not a multiple of 3."
+            yield f"{feature_name!r} has length {length} which is not a multiple of 3."
 
 
 def _read_nuc_annotation_from_gff(record, reference):

tests/functional/translate/cram/basic-error-checking.t

@@ -30,8 +30,8 @@ Gene length not divisible by 3
   >  --reference-sequence invalid.gff \
   >  --output-node-data "aa_muts.json"
   ERROR: Reference file 'invalid.gff' failed validation:
-      Gene length of 'gene1' is not a multiple of 3.
-      Gene length of 'gene2' is not a multiple of 3.
+      'gene1' has length 14 which is not a multiple of 3.
+      'gene2' has length 13 which is not a multiple of 3.
   [2]
 
 Gene with compound location not divisible by 3
@@ -60,5 +60,5 @@ Gene with compound location not divisible by 3
   .* (re)
   .* (re)
   ERROR: Reference file 'invalid.gb' failed validation:
-      Gene length of 'test_gene' is not a multiple of 3.
+      'test_gene' has length 26 which is not a multiple of 3.
   [2]