Error when building Mate for Slackware 14.2

I want to build mate for my Slackware 14.2. When I run the script that builds dependencies, I get this error

```
Executing install script for libpeas-1.20.0-x86_64-1_msb.txz.
Package libpeas-1.20.0-x86_64-1_msb.txz installed.

Package libpeas-1.20.0-x86_64-1_msb upgraded with new package /tmp/libpeas-1.20.0-x86_64-1_msb.txz.

--2020-11-29 15:10:22-- ftp://ftp.gnome.org/pub/GNOME/source...-3.18.4.tar.xz
=> 'gtksourceview-3.18.4.tar.xz'
Resolving ftp.gnome.org (ftp.gnome.org)... 8.43.85.29, 8.43.85.13, 8.43.85.14, ...
Connecting to ftp.gnome.org (ftp.gnome.org)|8.43.85.29|:21... failed: No route to host.
Connecting to ftp.gnome.org (ftp.gnome.org)|8.43.85.13|:21... failed: No route to host.
Connecting to ftp.gnome.org (ftp.gnome.org)|8.43.85.14|:21... failed: No route to host.
Connecting to ftp.gnome.org (ftp.gnome.org)|2620:52:3:1:5054:ff:fedd:5ad0|:21... failed: Network is unreachable.
Connecting to ftp.gnome.org (ftp.gnome.org)|2620:52:3:1:5054:ff:fede:8714|:21... failed: Network is unreachable.
Connecting to ftp.gnome.org (ftp.gnome.org)|2620:52:3:1:5054:ff:fe0d:ee0f|:21... failed: Network is unreachable.
tar: /root/msb/deps/gtksourceview3/gtksourceview-3.18.4.tar.xz: Cannot open: No such file or directory
tar: Error is not recoverable: exiting now
```
At first I thought it was a network error, but when I re-ran the script, it came to the same place with the same error again