Django 2.2 + AttributeError: 'str' object has no attribute 'decode'

Question

We have done Django Upgrade from 1.11 to 2.2 version, we have almost completed, but there is one issue is present, when we run migrations by using the command python manage.py makemigrations then we are getting following error.

but when we follow the below link issue is resolved.

Migrations error in django 2; AttributeError: 'str' object has no attribute 'decode'

but, I just want to know is there any other way to resolve this issue? I am feeling like there will be library to update which is causing this issue?

When we add manually as suggested in above link, its working fine, but we have docker integration to the project, then it will fail?

same issue is not happening with below django 2.2 and above 2.2.20 versions.

Error message is:

(env4) user2@SK385 pro % python manage.py makemigrations
Traceback (most recent call last):
  File "manage.py", line 21, in <module>
    main()
  File "manage.py", line 17, in main
    execute_from_command_line(sys.argv)
  File "/Users/user2/Desktop/env4/lib/python3.7/site-packages/django/core/management/__init__.py", line 381, in execute_from_command_line
    utility.execute()
  File "/Users/user2/Desktop/env4/lib/python3.7/site-packages/django/core/management/__init__.py", line 375, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/Users/user2/Desktop/env4/lib/python3.7/site-packages/django/core/management/base.py", line 323, in run_from_argv
    self.execute(*args, **cmd_options)
  File "/Users/user2/Desktop/env4/lib/python3.7/site-packages/django/core/management/base.py", line 364, in execute
    output = self.handle(*args, **options)
  File "/Users/user2/Desktop/env4/lib/python3.7/site-packages/django/core/management/base.py", line 83, in wrapped
    res = handle_func(*args, **kwargs)
  File "/Users/user2/Desktop/env4/lib/python3.7/site-packages/django/core/management/commands/makemigrations.py", line 101, in handle
    loader.check_consistent_history(connection)
  File "/Users/user2/Desktop/env4/lib/python3.7/site-packages/django/db/migrations/loader.py", line 283, in check_consistent_history
    applied = recorder.applied_migrations()
  File "/Users/user2/Desktop/env4/lib/python3.7/site-packages/django/db/migrations/recorder.py", line 73, in applied_migrations
    if self.has_table():
  File "/Users/user2/Desktop/env4/lib/python3.7/site-packages/django/db/migrations/recorder.py", line 56, in has_table
    return self.Migration._meta.db_table in self.connection.introspection.table_names(self.connection.cursor())
  File "/Users/user2/Desktop/env4/lib/python3.7/site-packages/ddtrace/contrib/django/db.py", line 65, in cursor
    return DbApiTracedCursor(conn._datadog_original_cursor(), pin)
  File "/Users/user2/Desktop/env4/lib/python3.7/site-packages/django/db/backends/base/base.py", line 256, in cursor
    return self._cursor()
  File "/Users/user2/Desktop/env4/lib/python3.7/site-packages/django/db/backends/base/base.py", line 233, in _cursor
    self.ensure_connection()
  File "/Users/user2/Desktop/env4/lib/python3.7/site-packages/django/db/backends/base/base.py", line 217, in ensure_connection
    self.connect()
  File "/Users/user2/Desktop/env4/lib/python3.7/site-packages/django/db/backends/base/base.py", line 197, in connect
    self.init_connection_state()
  File "/Users/user2/Desktop/env4/lib/python3.7/site-packages/django/db/backends/mysql/base.py", line 231, in init_connection_state
    if self.features.is_sql_auto_is_null_enabled:
  File "/Users/user2/Desktop/env4/lib/python3.7/site-packages/django/utils/functional.py", line 80, in __get__
    res = instance.__dict__[self.name] = self.func(instance)
  File "/Users/user2/Desktop/env4/lib/python3.7/site-packages/django/db/backends/mysql/features.py", line 82, in is_sql_auto_is_null_enabled
    cursor.execute('SELECT @@SQL_AUTO_IS_NULL')
  File "/Users/user2/Desktop/env4/lib/python3.7/site-packages/ddtrace/contrib/dbapi/__init__.py", line 90, in execute
    return self._trace_method(self.__wrapped__.execute, self._self_datadog_name, query, {}, query, *args, **kwargs)
  File "/Users/user2/Desktop/env4/lib/python3.7/site-packages/ddtrace/contrib/dbapi/__init__.py", line 44, in _trace_method
    return method(*args, **kwargs)
  File "/Users/user2/Desktop/env4/lib/python3.7/site-packages/django/db/backends/utils.py", line 103, in execute
    sql = self.db.ops.last_executed_query(self.cursor, sql, params)
  File "/Users/user2/Desktop/env4/lib/python3.7/site-packages/django/db/backends/mysql/operations.py", line 146, in last_executed_query
    query = query.decode(errors='replace')
AttributeError: 'str' object has no attribute 'decode'
user2

Answer 1

I think you're hitting this issue because you're using PyMySQL.

The issue was fixed in ticket 30380, but wasn't backported to Django 2.2.X because Django doesn't officially support PyMySQL.

Some options are:

• Upgrade to Django 3.0.X+
• Switch from PyMySQL to mysqlclient
• patch your version of Django 2.2 (see the fix here)