sslutil: inform the user about how to fix an incomplete certificate chain

This is a Windows only thing.  Unfortunately, the socket is closed at this point
(so the certificate is unavailable to check the chain).  That means it's printed
out when verification fails as a guess, on the assumption that 1) most of the
time verification won't fail, and 2) sites using expired or certs that are too
new will be rare.  Maybe this is an argument for adding more functionality to
debugssl, to test for problems and print certificate info.  Or maybe it's an
argument for bundling certificates with the Windows builds.  That idea was set
aside when the enhanced SSL code went in last summer, and it looks like there
were issues with using certifi on Windows anyway[1].

This was tested by deleting the certificate out of certmgr.msc > "Third-Party
Root Certification Authorities" > "Certificates", seeing `hg pull` fail (with
the new message), trying this command, and then successfully performing the pull
command.

[1] https://www.mercurial-scm.org/pipermail/mercurial-devel/2016-October/089573.html

mercurial/sslutil.py

@@ -475,6 +475,12 @@ def wrapsocket(sock, keyfile, certfile, ui, serverhostname=None):
                     ui.warn(_(
                         '(see https://mercurial-scm.org/wiki/SecureConnections '
                         'for more info)\n'))
+
+            elif (e.reason == 'CERTIFICATE_VERIFY_FAILED' and
+                pycompat.osname == 'nt'):
+
+                ui.warn(_('(the full certificate chain may not be available '
+                          'locally; see "hg help debugssl")\n'))
         raise
 
     # check if wrap_socket failed silently because socket had been

tests/test-https.t

@@ -84,6 +84,7 @@ we are able to load CA certs.
   $ hg clone https://localhost:$HGPORT/ copy-pull
   warning: connecting to localhost using legacy security technology (TLS 1.0); see https://mercurial-scm.org/wiki/SecureConnections for more info (?)
   (using CA certificates from *; if you see this message, your Mercurial install is not properly configured; see https://mercurial-scm.org/wiki/SecureConnections for how to configure Mercurial to avoid this message) (glob) (?)
+  (the full certificate chain may not be available locally; see "hg help debugssl") (windows !)
   abort: error: *certificate verify failed* (glob)
   [255]
 #endif
@@ -128,6 +129,7 @@ A per-host certificate mismatching the server will fail verification
   $ hg --config hostsecurity.localhost:verifycertsfile="$CERTSDIR/client-cert.pem" clone https://localhost:$HGPORT/
   warning: connecting to localhost using legacy security technology (TLS 1.0); see https://mercurial-scm.org/wiki/SecureConnections for more info (?)
   (an attempt was made to load CA certificates but none were loaded; see https://mercurial-scm.org/wiki/SecureConnections for how to configure Mercurial to avoid this error)
+  (the full certificate chain may not be available locally; see "hg help debugssl") (windows !)
   abort: error: *certificate verify failed* (glob)
   [255]
 #else
@@ -295,6 +297,7 @@ cacert mismatch
   $ hg -R copy-pull pull --config web.cacerts="$CERTSDIR/pub-other.pem"
   pulling from https://localhost:$HGPORT/
   warning: connecting to localhost using legacy security technology (TLS 1.0); see https://mercurial-scm.org/wiki/SecureConnections for more info (?)
+  (the full certificate chain may not be available locally; see "hg help debugssl") (windows !)
   abort: error: *certificate verify failed* (glob)
   [255]
   $ hg -R copy-pull pull --config web.cacerts="$CERTSDIR/pub-other.pem" \
@@ -313,6 +316,7 @@ Test server cert which isn't valid yet
   > https://localhost:$HGPORT1/
   pulling from https://localhost:$HGPORT1/
   warning: connecting to localhost using legacy security technology (TLS 1.0); see https://mercurial-scm.org/wiki/SecureConnections for more info (?)
+  (the full certificate chain may not be available locally; see "hg help debugssl") (windows !)
   abort: error: *certificate verify failed* (glob)
   [255]
 
@@ -324,6 +328,7 @@ Test server cert which no longer is valid
   > https://localhost:$HGPORT2/
   pulling from https://localhost:$HGPORT2/
   warning: connecting to localhost using legacy security technology (TLS 1.0); see https://mercurial-scm.org/wiki/SecureConnections for more info (?)
+  (the full certificate chain may not be available locally; see "hg help debugssl") (windows !)
   abort: error: *certificate verify failed* (glob)
   [255]
 
@@ -578,12 +583,14 @@ Test https with cert problems through proxy
   > --config web.cacerts="$CERTSDIR/pub-other.pem"
   pulling from https://localhost:$HGPORT/
   warning: connecting to localhost using legacy security technology (TLS 1.0); see https://mercurial-scm.org/wiki/SecureConnections for more info (?)
+  (the full certificate chain may not be available locally; see "hg help debugssl") (windows !)
   abort: error: *certificate verify failed* (glob)
   [255]
   $ http_proxy=http://localhost:$HGPORT1/ hg -R copy-pull pull \
   > --config web.cacerts="$CERTSDIR/pub-expired.pem" https://localhost:$HGPORT2/
   pulling from https://localhost:$HGPORT2/
   warning: connecting to localhost using legacy security technology (TLS 1.0); see https://mercurial-scm.org/wiki/SecureConnections for more info (?)
+  (the full certificate chain may not be available locally; see "hg help debugssl") (windows !)
   abort: error: *certificate verify failed* (glob)
   [255]
 
@@ -619,6 +626,7 @@ without client certificate:
 
   $ P="$CERTSDIR" hg id https://localhost:$HGPORT/
   warning: connecting to localhost using legacy security technology (TLS 1.0); see https://mercurial-scm.org/wiki/SecureConnections for more info (?)
+  (the full certificate chain may not be available locally; see "hg help debugssl") (windows !)
   abort: error: *handshake failure* (glob)
   [255]
 

tests/test-patchbomb-tls.t

@@ -67,6 +67,7 @@ we are able to load CA certs:
   
   warning: connecting to localhost using legacy security technology (TLS 1.0); see https://mercurial-scm.org/wiki/SecureConnections for more info (?)
   (using CA certificates from *; if you see this message, your Mercurial install is not properly configured; see https://mercurial-scm.org/wiki/SecureConnections for how to configure Mercurial to avoid this message) (glob) (?)
+  (the full certificate chain may not be available locally; see "hg help debugssl") (windows !)
   (?i)abort: .*?certificate.verify.failed.* (re)
   [255]
 
@@ -118,6 +119,7 @@ With invalid certificates:
   
   
   warning: connecting to localhost using legacy security technology (TLS 1.0); see https://mercurial-scm.org/wiki/SecureConnections for more info (?)
+  (the full certificate chain may not be available locally; see "hg help debugssl") (windows !)
   (?i)abort: .*?certificate.verify.failed.* (re)
   [255]