This is a continuation of SAT-26026 on the libdnf side of things.

What were you trying to do that didn't work?

A customer has a local repository with metadata in .zst format installed on a Sat 6.14 system (based on RHEL8.10). Because it's a Sat system, a specific libsolv-0.7.22-4.el8pc package is installed, which doesn't have zstd support inside, hence make solv_xfopen() function return 0.
This leads to having any dnf command crash in assertion:

# yum update
[...]
platform-python: /builddir/build/BUILD/libdnf-0.63.0/libdnf/dnf-sack.cpp:781: gboolean load_yum_repo(DnfSack*, HyRepo, GError**): Assertion `fp_primary' failed.
Aborted (core dumped)

 
This assertion occurs because libdnf code assumes that solv_xfopen() never fails, which is just wrong (as seen above, see also analysis in SAT-26026):

 722 static gboolean
 723 load_yum_repo(DnfSack *sack, HyRepo hrepo, GError **error)
 724 {
 :
 780         fp_primary = solv_xfopen(primary.c_str(), "r");
 781         assert(fp_primary);
 :

Please harden this code to properly handle the possible error occurring on line 780.

Please provide the package NVR for which bug is seen:

libdnf-0.63.0-19.el8.x86_64

How reproducible:

Always

Steps to reproduce

1. Setup a local repository with .zst metadata
2. Install Sat 6.14 specific libsolv-0.7.22-4.el8pc
3. Perform a yum update command

Expected results

Some self-explanatory error message (to be passed by libsolv itself to libdnf)

Actual results

Assertion