pip 低版本版本导致ss不能下载

报错信息如下，连接不上。

Collecting ***

  Retrying (Retry(total=4, connect=None, read=None, redirect=None)) after connection broken by 'NewConnectionError('<pip._vendor.requests.packages.urllib3.connection.VerifiedHTTPSConnection object at 0x10e6a3e48>: Failed to establish a new connection: [Errno 65] No route to host',)': /simple/***/

  Retrying (Retry(total=3, connect=None, read=None, redirect=None)) after connection broken by 'NewConnectionError('<pip._vendor.requests.packages.urllib3.connection.VerifiedHTTPSConnection object at 0x10e6a3d68>: Failed to establish a new connection: [Errno 65] No route to host',)': /simple/***/

  Retrying (Retry(total=2, connect=None, read=None, redirect=None)) after connection broken by 'NewConnectionError('<pip._vendor.requests.packages.urllib3.connection.VerifiedHTTPSConnection object at 0x10e6a3080>: Failed to establish a new connection: [Errno 65] No route to host',)': /simple/***/

  Retrying (Retry(total=1, connect=None, read=None, redirect=None)) after connection broken by 'NewConnectionError('<pip._vendor.requests.packages.urllib3.connection.VerifiedHTTPSConnection object at 0x10e6a31d0>: Failed to establish a new connection: [Errno 65] No route to host',)': /simple/***/

  Retrying (Retry(total=0, connect=None, read=None, redirect=None)) after connection broken by 'NewConnectionError('<pip._vendor.requests.packages.urllib3.connection.VerifiedHTTPSConnection object at 0x10e6a3518>: Failed to establish a new connection: [Errno 65] No route to host',)': /simple/***/

  Could not find a version that satisfies the requirement *** (from versions: )

No matching distribution found for ***

解决：升级

pip install --upgrade pip