使用pip install 命令时，提示 Using cached解决方案

PS C:\Users\rHotD\Documents\GitHub> pip install -r .\requirements.txt
Collecting asn1crypto==0.22.0 (from -r .\requirements.txt (line 1))
  Using cached asn1crypto-0.22.0-py2.py3-none-any.whl
Collecting attrs==17.2.0 (from -r .\requirements.txt (line 2))
  Using cached attrs-17.2.0-py2.py3-none-any.whl
Collecting Automat==0.6.0 (from -r .\requirements.txt (line 3))
  Using cached Automat-0.6.0-py2.py3-none-any.whl
Collecting beautifulsoup4==4.5.3 (from -r .\requirements.txt (line 4))
  Using cached beautifulsoup4-4.5.3-py3-none-any.whl
Collecting cffi==1.10.0 (from -r .\requirements.txt (line 5))
  Using cached cffi-1.10.0-cp36-cp36m-win32.whl
Collecting constantly==15.1.0 (from -r .\requirements.txt (line 6))
  Using cached constantly-15.1.0-py2.py3-none-any.whl
Collecting cryptography==1.8.1 (from -r .\requirements.txt (line 7))
  Using cached cryptography-1.8.1-cp36-cp36m-win32.whl
Collecting cssselect==1.0.1 (from -r .\requirements.txt (line 8))
  Using cached cssselect-1.0.1-py2.py3-none-any.whl
Collecting cycler==0.10.0 (from -r .\requirements.txt (line 9))
  Using cached cycler-0.10.0-py2.py3-none-any.whl
Collecting Django==1.10.6 (from -r .\requirements.txt (line 10))
  Using cached Django-1.10.6-py2.py3-none-any.whl
Collecting django-crispy-forms==1.6.1 (from -r .\requirements.txt (line 11))
  Using cached django_crispy_forms-1.6.1-py2.py3-none-any.whl
Collecting django-formtools==2.0 (from -r .\requirements.txt (line 12))
  Using cached django_formtools-2.0-py2.py3-none-any.whl
Collecting django-pure-pagination==0.3.0 (from -r .\requirements.txt (line 13))

解决办法，删掉 pip/cache/ 目录下的所有文件夹

Clear the cache directory where appropriate for your system

https://stackoverflow.com/questions/9510474/removing-pips-cache

PS C:\Users\rHotD\Documents\GitHub> pip install -r .\requirements.txt
Collecting asn1crypto==0.22.0 (from -r .\requirements.txt (line 1))
  Downloading asn1crypto-0.22.0-py2.py3-none-any.whl (97kB)
    100% |████████████████████████████████| 102kB 109kB/s
Collecting attrs==17.2.0 (from -r .\requirements.txt (line 2))
  Downloading attrs-17.2.0-py2.py3-none-any.whl
Collecting Automat==0.6.0 (from -r .\requirements.txt (line 3))
  Downloading Automat-0.6.0-py2.py3-none-any.whl
Collecting beautifulsoup4==4.5.3 (from -r .\requirements.txt (line 4))
  Downloading beautifulsoup4-4.5.3-py3-none-any.whl (85kB)
    100% |████████████████████████████████| 92kB 684kB/s
Collecting cffi==1.10.0 (from -r .\requirements.txt (line 5))
  Downloading cffi-1.10.0-cp36-cp36m-win32.whl (149kB)
    100% |████████████████████████████████| 153kB 365kB/s
Collecting constantly==15.1.0 (from -r .\requirements.txt (line 6))
  Downloading constantly-15.1.0-py2.py3-none-any.whl
Collecting cryptography==1.8.1 (from -r .\requirements.txt (line 7))
  Downloading cryptography-1.8.1-cp36-cp36m-win32.whl (1.1MB)
    100% |████████████████████████████████| 1.1MB 828kB/s
Collecting cssselect==1.0.1 (from -r .\requirements.txt (line 8))