Enter chroot can return an error code on cleanup. We make cleanup best effort

src/scripts/enter_chroot.sh

 #!/bin/bash
 
 # Copyright (c) 2009 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # Script to enter the chroot environment
 
 # Load common constants.  This should be the first executable line.
 # The path to common.sh should be relative to your script's location.
@@ skipping 116 matching lines @@
           echo "This may impact chromium build."
         fi
       fi
     fi
   ) 200>>"$LOCKFILE"
 }
 
 function teardown_env {
   # Only teardown if we're the last enter_chroot to die
 
+  # We should not return with an error if cleanup has an error.  Cleanup is
+  # best effort only.
+  set +e
+
   (
     flock 200
 
     # check each pid in $LOCKFILE to see if it's died unexpectedly
     TMP_LOCKFILE="$LOCKFILE.tmp"
 
     echo -n > "$TMP_LOCKFILE"  # Erase/reset temp file
     cat "$LOCKFILE" | while read PID; do
       if [ "$PID" = "$$" ]; then
         # ourself, leave PROC_NAME empty
@@ skipping 71 matching lines @@
 
 # Run command or interactive shell.  Also include the non-chrooted path to
 # the source trunk for scripts that may need to print it (e.g.
 # build_image.sh).
 sudo chroot "$FLAGS_chroot" sudo -i -u $USER $CHROOT_PASSTHRU \
   EXTERNAL_TRUNK_PATH="${FLAGS_trunk}" LANG=C "$@"
 
 # Remove trap and explicitly unmount
 trap - EXIT
 teardown_env