fix(api): Fix failing weak password test

[paulespinosa]

Closes #759

What changes did you make?

• Make admin_controller.remove_user function only attempt to delete a Cognito user when that operation is requested.
• Formatted the code using yapf.

Rationale behind the changes?

• A weak password test was failing because this function was throwing an AuthError because the remove_user function was attempting to remove a non-existing user from Cognito.

Testing done for these changes

• I re-ran tox in a virtual environment

What did you learn or can share that is new?(optional)

• The authorization/user management code could be redesigned.
• The API code needs to follow consistent formatting and style.

[erikguntner]

Thanks @paulespinosa! This looks great.