Hello,
This week, I tried to build a fresh GTK-OSX build on macOS HS.
I'have got many errors with 
ftp.gnu.org, for instance:
curl: (56) response reading failed
curl: (7) Failed to connect to 
ftp.gnu.org port 21: Operation timed out
There is a notice on 
https://ftp.gnu.org:"NOTICE (Updated October 13 2017):
Because of security concerns with plaintext protocols, we still
intend to disable the FTP protocol for downloads on this server
(downloads would still be available over HTTP and HTTPS), but we
will not be doing it on November 1, 2017, as previously announced
here. We will be sharing our reasons and offering a chance to
comment on this issue soon; watch this space for details.
If you maintain scripts used to access 
ftp.gnu.org over FTP,
we strongly encourage you to change them to use HTTPS instead."
What to do to switch to https as written?