fix linter errors

app/main/forms.py

@@ -506,7 +506,7 @@ class ServiceSmsSender(Form):
         ]
     )
 
-    def validate_sms_sender(form, field):
+    def validate_sms_sender(self, field):
         if field.data and not re.match(r'^[a-zA-Z0-9\s]+$', field.data):
             raise ValidationError('Use letters and numbers only')
 
@@ -520,7 +520,7 @@ class ServiceLetterContactBlockForm(Form):
     )
     is_default = BooleanField("Set as your default address")
 
-    def validate_letter_contact_block(form, field):
+    def validate_letter_contact_block(self, field):
         line_count = field.data.strip().count('\n')
         if line_count >= 10:
             raise ValidationError(

app/main/views/dashboard.py

@@ -80,7 +80,7 @@ def template_history(service_id):
 
     months = [
         {
-            'name': YYYY_MM_to_datetime(month).strftime('%B'),
+            'name': yyyy_mm_to_datetime(month).strftime('%B'),
             'templates_used': aggregate_usage(
                 format_template_stats_to_list(stats.get(month)), sort_key='requested_count'
             ),
@@ -310,14 +310,14 @@ def format_monthly_stats_to_list(historical_stats):
     return sorted((
         dict(
             date=key,
-            future=YYYY_MM_to_datetime(key) > datetime.utcnow(),
-            name=YYYY_MM_to_datetime(key).strftime('%B'),
+            future=yyyy_mm_to_datetime(key) > datetime.utcnow(),
+            name=yyyy_mm_to_datetime(key).strftime('%B'),
             **aggregate_status_types(value)
         ) for key, value in historical_stats.items()
     ), key=lambda x: x['date'])
 
 
-def YYYY_MM_to_datetime(string):
+def yyyy_mm_to_datetime(string):
     return datetime(int(string[0:4]), int(string[5:7]), 1)