Seems to be the same issue like in bug 1060231 but nobody cared for that one as
it has been reported for the wrong assignee.

I have my Leap 42.3 fixes repo configured like this:
> https://download.opensuse.org/repositories/home:/sparschauer:/leap42.3_fixes/openSUSE_Leap_42.3
Local name: fixes

I run
> zypper dup --allow-vendor-change -r fixes
to pull in my temporary fix packages.

zypper output:
> Retrieving package libgvnc-1_0-0-0.6.0-3.1.0.FIX.1099697.x86_64    (1/11), 103,5 KiB (284,2 KiB unpacked)
> Retrieving: libgvnc-1_0-0-0.6.0-3.1.0.FIX.1099697.x86_64.rpm .....................................[error]
Download (curl) error for
'https://download.opensuse.org/repositories/home:/sparschauer:/leap42.3_fixes/openSUSE_Leap_42.3/x86_64/libgvnc-1_0-0-0.6.0-3.1.0.FIX.1099697.x86_64.rpm':
> Error code:  Bad URL
> Error message: Protocol http not supported or disabled in libcurl
> 
> Abort, retry, ignore? [a/r/i/...? shows all options] (a):

Checked in the browser:
> https://download.opensuse.org/repositories/home:/sparschauer:/leap42.3_fixes/openSUSE_Leap_42.3/x86_64/libgvnc-1_0-0-0.6.0-3.1.0.FIX.1099697.x86_64.rpm

It tries to download from http://ftp.icm.edu.pl

Can you please fix that no http mirror is used for https? TIA