Error while running wolfram_client.aquery

lately I have been getting this weird error in this file while running `wolfram_client.aquery()` when i ask a question like "Define something".

The Error is as below
```
Traceback (most recent call last):
File "", line 1, in
File "c:\Users\myUser\dev\app\venv\Lib\site-packages\wolframalpha\__init__.py", line 129, in aquery
assert resp.headers['Content-Type'] == 'text/xml;charset=utf-8'
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError
```

I wasn't getting this earlier.

I am using wolfram client version wolframalpha==5.1.3

Start at wolframalpha/__init__.py, line 129, and reproduce wolfram_client.aquery() with a question such as "Define something" using wolframalpha==5.1.3. Inspect the response Content-Type that triggers the assertion and determine the expected handling; done means the query no longer fails for the reported response and the behavior is covered by a regression test.

Written by the indexing model from the issue text.