fix: use msgcat instead of tail

tail can produce duplicate messages in django.po which will raise an error in compilemessages

Refs: FC-0012 OEP-58

Makefile

@@ -58,19 +58,22 @@ upgrade: $(COMMON_CONSTRAINTS_TXT)  ## update the requirements/*.txt files with
 ## Localization targets
 
 WORKING_DIR := lti_consumer
-EXTRACT_DIR := $(WORKING_DIR)/translations/en/LC_MESSAGES
+EXTRACT_DIR := $(WORKING_DIR)/conf/locale/en/LC_MESSAGES
 JS_COMPILE_DIR := $(WORKING_DIR)/public/js/translations
-EXTRACTED_DJANGO := $(EXTRACT_DIR)/django-partial.po
-EXTRACTED_DJANGOJS := $(EXTRACT_DIR)/djangojs-partial.po
-EXTRACTED_TEXT := $(EXTRACT_DIR)/django.po
+EXTRACTED_DJANGO_PARTIAL := $(EXTRACT_DIR)/django-partial.po
+EXTRACTED_DJANGOJS_PARTIAL := $(EXTRACT_DIR)/djangojs-partial.po
+EXTRACTED_DJANGO := $(EXTRACT_DIR)/django.po
 
 extract_translations: ## extract strings to be translated, outputting .po files
 	cd $(WORKING_DIR) && i18n_tool extract
-	mv $(EXTRACTED_DJANGO) $(EXTRACTED_TEXT)
-	tail -n +20 $(EXTRACTED_DJANGOJS) >> $(EXTRACTED_TEXT)
-	rm $(EXTRACTED_DJANGOJS)
-	sed -i'' -e 's/nplurals=INTEGER/nplurals=2/' $(EXTRACTED_TEXT)
-	sed -i'' -e 's/plural=EXPRESSION/plural=\(n != 1\)/' $(EXTRACTED_TEXT)
+	mv $(EXTRACTED_DJANGO_PARTIAL) $(EXTRACTED_DJANGO)
+	# Safely concatenate djangojs if it exists
+	if test -f $(EXTRACTED_DJANGOJS_PARTIAL); then \
+	  msgcat $(EXTRACTED_DJANGO) $(EXTRACTED_DJANGOJS_PARTIAL) -o $(EXTRACTED_DJANGO) && \
+	  rm $(EXTRACTED_DJANGOJS_PARTIAL); \
+	fi
+	sed -i'' -e 's/nplurals=INTEGER/nplurals=2/' $(EXTRACTED_DJANGO)
+	sed -i'' -e 's/plural=EXPRESSION/plural=\(n != 1\)/' $(EXTRACTED_DJANGO)
 
 compile_translations: ## compile translation files, outputting .mo files for each supported language
 	cd $(WORKING_DIR) && i18n_tool generate