Support unittest.mock.ANY in header comparison

[dimaqq]

I'm testing a starlette app, let's pretend it's httpbin:

async def test_no_auth(client, services):                                               
    r = client.get("/bearer")                                                           
    assert r.status_code == 401                                                         
    assert r.headers == {                                                         
        "access-control-allow-origin": "*",                                             
        "access-control-allow-methods": "*",                                            
        "access-control-max-age": "86400",                                              
        "content-type": ANY,                                                            
        "x-content-type-options": ANY,                                                  
    }     

This fails with E AttributeError: '_ANY' object has no attribute 'encode'

For now I work around this by "casting" the magic header dict to an actual dict:

async def test_no_auth(client, services):                                               
    r = client.get("/bearer")                                                           
    assert r.status_code == 401                                                         
    assert dict(r.headers) == {                                                         
        "access-control-allow-origin": "*",                                             
        "access-control-allow-methods": "*",                                            
        "access-control-max-age": "86400",                                              
        "content-type": ANY,                                                            
        "x-content-type-options": ANY,                                                  
    }     

Then the comparison works and test is happy.