Dear Maintainer,

Ketchup as in Debian Buster does not support kernel versions 5.x.y.

For basic support this short patch is sufficient:
#############################
--- /usr/bin/ketchup    2017-01-23 07:55:18.000000000 +0100
+++ ./bin/ketchup       2019-12-05 10:28:49.000000001 +0100
@@ -103,7 +103,7 @@
     return args

 # Default values
-kernel_url = 'http://www.kernel.org/pub/linux/kernel'
+kernel_url = 'https://cdn.kernel.org/pub/linux/kernel'
 archive = os.environ["HOME"] + "/.ketchup"
 rename_prefix = 'linux-'
 rename_with_localversion = False
@@ -982,6 +982,10 @@
           ["%(kernel_url)s" + "/v4.x" + "/patch-%(prebase)s.xz"],
           r'patch-(.*?).xz',
           1, "current stable kernel series"),
+    '5': (latest_dir,
+          ["%(kernel_url)s" + "/v5.x" + "/patch-%(prebase)s.xz"],
+          r'patch-(.*?).xz',
+          1, "current stable kernel series"),

     }
#############################
Best regards,
Andreas Hirczy

Here is a modified version that includes the previous patch for 5.x.Y
plus support for python 3.8

Dear submitter,

as the package ketchup has just been removed from the Debian archive
unstable we hereby close the associated bug reports.  We are sorry
that we couldn't deal with your issue properly.

For details on the removal, please see https://bugs.debian.org/1008702

The version of this package that was in Debian prior to this removal
can still be found using http://snapshot.debian.org/.

Please note that the changes have been done on the master archive and
will not propagate to any mirrors until the next dinstall run at the
earliest.

This message was generated automatically; if you believe that there is
a problem with it please contact the archive administrators by mailing
ftpmaster@ftp-master.debian.org.

Debian distribution maintenance software
pp.
Thorsten Alteholz (the ftpmaster behind the curtain)