Python 3.9 support for installing extra package

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I can't install opencv-python, which is required by the extra package, on python 3.9.

$ python -VV
Python 3.9.0 (default, Oct  6 2020, 21:52:53) 
[GCC 8.3.0]

$ pip install anymotion-sdk[cv]
Collecting anymotion-sdk[cv]
  Downloading anymotion_sdk-1.2.2-py3-none-any.whl (13 kB)
Collecting requests<3.0.0,>=2.22.0
  Downloading requests-2.24.0-py2.py3-none-any.whl (61 kB)
     |████████████████████████████████| 61 kB 329 kB/s 
ERROR: Could not find a version that satisfies the requirement opencv-python<4.3,>=4.2; extra == "cv" (from anymotion-sdk[cv]) (from versions: 3.4.10.37, 3.4.11.39, 3.4.11.41, 3.4.11.43, 4.3.0.38, 4.4.0.40, 4.4.0.42, 4.4.0.44)
ERROR: No matching distribution found for opencv-python<4.3,>=4.2; extra == "cv" (from anymotion-sdk[cv])

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waiting for: opencv/opencv-python#382