Add more failure contexts for exec_in_host_mountns

Signed-off-by: John Eckersberg <[email protected]>

lib/src/install.rs

@@ -704,12 +704,16 @@ pub(crate) fn exec_in_host_mountns(args: &[std::ffi::OsString]) -> Result<()> {
         .split_first()
         .ok_or_else(|| anyhow::anyhow!("Missing command"))?;
     tracing::trace!("{cmd:?} {args:?}");
-    let pid1mountns = std::fs::File::open("/proc/1/ns/mnt")?;
+    let pid1mountns = std::fs::File::open("/proc/1/ns/mnt").context("open pid1 mountns")?;
     nix::sched::setns(pid1mountns.as_fd(), nix::sched::CloneFlags::CLONE_NEWNS).context("setns")?;
     rustix::process::chdir("/").context("chdir")?;
     // Work around supermin doing chroot() and not pivot_root
     // https://github.com/libguestfs/supermin/blob/5230e2c3cd07e82bd6431e871e239f7056bf25ad/init/init.c#L288
-    if !Utf8Path::new("/usr").try_exists()? && Utf8Path::new("/root/usr").try_exists()? {
+    if !Utf8Path::new("/usr").try_exists().context("/usr")?
+        && Utf8Path::new("/root/usr")
+            .try_exists()
+            .context("/root/usr")?
+    {
         tracing::debug!("Using supermin workaround");
         rustix::process::chroot("/root").context("chroot")?;
     }