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

Example 1: 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

Example 2: 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