seeed interface: fix fileno issue with windows

[Gussy]

Environment:

• Python: 3.8.2
• Windows-10-10.0.18362-SP0

Issue
When using the seeedstudio interface on Linux or MacOS, I'm able to connect to the interface and send/receive messages.
When running the same script on Windows 10 the following error is thrown:

Traceback (most recent call last):
  File "<redacted>.py", line 264, in <module>
  File "<redacted>.py", line 44, in __init__
  File "can\notifier.py", line 56, in __init__
  File "can\notifier.py", line 66, in add_bus
  File "can\interfaces\seeedstudio\seeedstudio.py", line 266, in fileno
io.UnsupportedOperation: fileno

From the python-serial docs, fileno() is only supported on Posix platforms.

The commit below fixes the issue for me, without breaking functionality on Linux, although I'm not sure if this is correct solution.

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The diff coverage is 33.33%.

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[bmeisels]

This has come up also with with slcan (#760).
and the solution chosen was to raise an error which will be caught by the notifier(#877).
Suggest you revise your solution in line with the change to notifier as i believe your current patch changes the behavior on Linux.
I would consider detecting explicitly if you are on windows.

[Gussy]

Thanks for the feedback @bmeisels.

I think that I understood what you're asking for based on those two PRs you linked to, so I went ahead and amended the commit.

[hardbyte]

This line now looks unreachable, and should be removed.

[Gussy]

@hardbyte I've amended the commit to remote that line 👍

[hardbyte]

Thanks!

Sorry it took me a long time to get back to this

[Gussy]

Is there anything I can do to help get this merged into develop?