ERROR-Could not build wheels for opencv-python which use PEP 517 and cannot be installed directly

1. pip install opencv-python时遇到如下问题：ERROR-Could not build wheels for opencv-python which use PEP 517 and cannot be installed directly
2. 解决方案：
   1. pip install opencv-python --no-use-pep517 ×
   2. pip install opencv-python --no-cache-dir √
3. 版本信息：
   1. Ubuntu：20.04
   2. python：3.7
   3. opencv-python：4.4.0.42
   4. pip：19.2.3