Make email_from and subject required attributes of the email_content schema.

Update the format_checkers to raise the specific exception that why the validator can handle multiple messages.
Which led to a refactor of build_error_message.

app/schema_validation/__init__.py

@@ -1,38 +1,45 @@
 import json
 
 from jsonschema import (Draft4Validator, ValidationError, FormatChecker)
-from notifications_utils.recipients import (validate_phone_number, validate_email_address)
+from notifications_utils.recipients import (validate_phone_number, validate_email_address, InvalidPhoneError,
+                                            InvalidEmailError)
 
 
 def validate(json_to_validate, schema):
     format_checker = FormatChecker()
 
-    @format_checker.checks('phone_number')
+    @format_checker.checks('phone_number', raises=InvalidPhoneError)
     def validate_schema_phone_number(instance):
-        return validate_phone_number(instance)
+        validate_phone_number(instance)
+        return True
 
-    @format_checker.checks('email_address')
+    @format_checker.checks('email_address', raises=InvalidEmailError)
     def validate_schema_email_address(instance):
-        return validate_email_address(instance)
+        validate_email_address(instance)
+        return True
 
     validator = Draft4Validator(schema, format_checker=format_checker)
     errors = list(validator.iter_errors(json_to_validate))
     if errors.__len__() > 0:
-        raise ValidationError(build_error_message(errors, schema))
+        raise ValidationError(build_error_message(errors))
     return json_to_validate
 
 
-def build_error_message(errors, schema):
+def build_error_message(errors):
     fields = []
     for e in errors:
-        field = "'{}' {}".format(e.path[0], e.schema.get('validationMessage')) if e.schema.get(
-            'validationMessage') else e.message
-        s = field.split("'")
-        field = {"error": "ValidationError", "message": "{}{}".format(s[1], s[2])}
-        fields.append(field)
+        field = "{} {}".format(e.path[0], e.schema.get('validationMessage')) if e.schema.get(
+            'validationMessage') else __format_message(e)
+        fields.append({"error": "ValidationError", "message": field})
     message = {
         "status_code": 400,
         "errors": fields
     }
 
     return json.dumps(message)
+
+
+def __format_message(e):
+    s = e.message.split("'")
+    msg = "{}{}".format(s[1], s[2])
+    return msg if not e.cause else "'{}' {}".format(e.path[0], e.cause.message)

app/v2/notifications/notification_schemas.py

@@ -80,7 +80,7 @@ email_content = {
         "body": {"type": "string"},
         "subject": {"type": "string"}
     },
-    "required": ["body"]
+    "required": ["body", "from_email", "subject"]
 }
 
 post_email_response = {