Bug#934171: sagemath: FTFBS with libreadline8

[Jonathan Wiltshire]

Source: sagemath
Version: 8.6-6
Severity: serious
Tags: ftbfs
Justification: FTBFS

In a rebuild for the readline transition sagemath fails to build
with the following error:

| Error: 22979 tests failed, up to 50 failures are tolerated

I tried to capture some of the log but it's so vast I gave up waiting
for it to download. You can see the full logs on the buildd page,
https://buildd.debian.org/status/package.php?p=sagemath


-- System Information:
Debian Release: 10.0
  APT prefers stable
  APT policy: (990, 'stable'), (500, 'oldstable-updates'), (500, 'unstable'), (500, 'oldstable')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 4.19.0-5-amd64 (SMP w/4 CPU cores)
Kernel taint flags: TAINT_OOT_MODULE, TAINT_UNSIGNED_MODULE
Locale: LANG=en_GB.utf8, LC_CTYPE=en_GB.utf8 (charmap=UTF-8), LANGUAGE=en_GB:en (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled