On Sat, 23 Sep 2017, Arthur Yu via curl-users wrote:

> SSL certificate problem: unable to get local issuer certificate

This usually indicates that the server (which I suppose is the HTTPS proxy in
your case) doesn't provide the intermediate certificate. If so, that's an
error on your proxy's behalf. It is usually less of a problem for browsers
since they cache such certificates and some even support AIA that lets them
download them on demand.

Using --proxy-insecure will of course work around that error but will make
your connection to the proxy **insecure**.

Here's a page describing intermediate certificates:

   https://blogs.cisco.com/security/where-is-my-intermediate-tls-certificate

-- 
  / daniel.haxx.se
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