$ ./curl --version
curl 7.66.0-DEV (Linux) libcurl/7.66.0-DEV OpenSSL/1.1.1c zlib/1.2.11
Release-Date: [unreleased]
Protocols: dict file ftp ftps gopher http https imap imaps ldap pop3 pop3s rtsp smb smbs smtp smtps telnet tftp 
Features: AsynchDNS HTTPS-proxy IPv6 Largefile libz NTLM SSL UnixSockets

$ ./curl -4 -v --proxy http://elite:3128/ --anyauth --fail 'http://unittest:password@cam-unittest-fixture.brightsign/~unittest/cgi-bin/auth-digest/make-large2.rb?maxage=0&bytes=310'
*   Trying 172.30.1.1:3128...
* TCP_NODELAY set
* Connected to elite (172.30.1.1) port 3128 (#0)
> GET http://cam-unittest-fixture.brightsign/~unittest/cgi-bin/auth-digest/make-large2.rb?maxage=0&bytes=310 HTTP/1.1
> Host: cam-unittest-fixture.brightsign
> User-Agent: curl/7.66.0-DEV
> Accept: */*
> Proxy-Connection: Keep-Alive
> 
* Mark bundle as not supporting multiuse
< HTTP/1.1 401 Unauthorized
< Date: Sat, 03 Aug 2019 20:29:09 GMT
< Server: Apache/2.4.25 (Debian)
< WWW-Authenticate: Digest realm="Unit test realm", nonce="O3jHUzyPBQA=850b0ffa9bc084fd1caa41a11f4a18aa90efa8db", algorithm=MD5, qop="auth"
< Content-Length: 478
< Content-Type: text/html; charset=iso-8859-1
< X-Cache: MISS from elite
< X-Cache-Lookup: HIT from elite:3128
< Via: 1.1 elite (squid/3.5.23)
< Connection: keep-alive
< 
* Ignoring the response-body
* Connection #0 to host elite left intact
* Issue another request to this URL: 'http://cam-unittest-fixture.brightsign/~unittest/cgi-bin/auth-digest/make-large2.rb?maxage=0&bytes=310'
* Found bundle for host elite: 0x560216d66f00 [serially]
* Hostname elite was found in DNS cache
*   Trying 172.30.1.1:3128...
* TCP_NODELAY set
* Connected to elite (172.30.1.1) port 3128 (#1)
> GET http://cam-unittest-fixture.brightsign/~unittest/cgi-bin/auth-digest/make-large2.rb?maxage=0&bytes=310 HTTP/1.1
> Host: cam-unittest-fixture.brightsign
> User-Agent: curl/7.66.0-DEV
> Accept: */*
> Proxy-Connection: Keep-Alive
> 
* Mark bundle as not supporting multiuse
* The requested URL returned error: 401 Unauthorized
* Closing connection 1
curl: (22) The requested URL returned error: 401 Unauthorized