fix python flask to handle comment block

Author: wing328

modules/swagger-codegen/src/main/java/io/swagger/codegen/languages/FlaskConnexionCodegen.java

@@ -336,4 +336,16 @@ public String toOperationId(String operationId) {
         //     addPet => add_pet
         return underscore(operationId);
     }
+
+    @Override
+    public String escapeQuotationMark(String input) {
+        // remove ' to avoid code injection
+        return input.replace("'", "");
+    }
+
+    @Override
+    public String escapeUnsafeCharacters(String input) {
+        // remove multiline comment
+        return input.replace("'''", "'_'_'");
+    }
 }