create_attachment not working

Hi!
I have started recently using your youtrack rest-api python client and I am currently having problems running the create_attachment() method to attach a binary file to an issue. I am using a command which is similar to the one I was using for the python 2.7 library, namely:
connectionobject.create_attachment("issueid", name='file.png', content=open('file.png','rb'),authorLogin="username")
I get an error "can't concat bytes to string".
Could you inform me if this method is working and, of possible, what is wrong with the command I am using? Thanks you!