Answers for "ERROR: Could not find a version that satisfies the requirement smtplib (from versions: none) ERROR: No matching distribution found for smtplib"

ERROR: Could not find a version that satisfies the requirement cv2 (from versions: none) ERROR: No matching distribution found for cv2

#Know the reason is really dumb, because the reason is that the package of CV2 is not called cv2 but called opencv-python

pip install opencv-python

#For python3:
pip3 install opencv-python

ERROR: Could not find a version that satisfies the requirement khabar>=1.1.3 (from cluster ensembles) (from version: 1.0) ERROR: No matching distribution found for hyper>=1.1.3

pip install ClusterEnsembles

pip error could not find a version that satisfies the requirement

$ curl https://pypi.org

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ERROR: Could not find a version that satisfies the requirement OpenGL (from versions: none) ERROR: No matching distribution found for OpenGL

pip install PyOpenGL #instead of OpenGL