Easier session scoped mock

[akeeman]

Mocker() usually mocks requests.Session.send. This results in a global effect.

This pr adds an argument to Mocker that allows to mock a single Session instance in a similar way, without the need to add custom adapters to a session and removing existing ones.

import requests
import requests_mock

my_session = requests.Session()
m = requests_mock.Mocker(session=my_session)
# ...

Use cases include mocking the session of several independent components that call the same end-point and we are only interested in the call order within a single component, but not in relation to each other.

[jamielennox]

So when i first wrote the library I expected many more people to be using a session so just had an adapter object. So requests_mock internally creates an adapter and you can mount that on your own session and then use the standard register_uri or .get() .post() on the adapter object.

[jamielennox]

This is not to say we shouldn't be able to still use the mocker method because that's more popular, but if you're looking to support your own use case easier this will work.

I'll try and find some time to review this soon. Thanks.

[akeeman]

After some reading in the documentation I found that too. It, however, is more work ("[...], without the need to add custom adapters to a session and removing existing ones.").
So I think it's great that using the adapter directly works. I just think it's easier for everyone to use the Mocker as a one stop shop. That's all.
Thanks in advance for taking a look at it. If you just don't think it's an improvement, feel free to say so.

[clslgrnc]

I am resolving conflicts in another PR: #133.

[jamielennox]

Going to take #133 in favor of this as it merges with other changes for this release.

Thank you for the contribution.