"swh fs mount" silently fails if fusermount3 isn't available
Unless "-f" is given
$ swh fs mount /tmp/foobar
WARNING:swh.core.cli:Could not load subcommand graph: module 'swh.graph.cli' has no attribute 'cli'
WARNING:swh.core.cli:Could not load subcommand search: module 'swh.search.cli' has no attribute 'cli'
WARNING:swh.core.cli:Could not load subcommand icinga_plugins: module 'swh.icinga_plugins.cli' has no attribute 'cli'
WARNING:swh.core.cli:Could not load subcommand indexer: module 'swh.indexer.cli' has no attribute 'cli'
$ ls /tmp/foobar
$ swh fs mount /tmp/foobar -f
WARNING:swh.core.cli:Could not load subcommand graph: module 'swh.graph.cli' has no attribute 'cli'
WARNING:swh.core.cli:Could not load subcommand search: module 'swh.search.cli' has no attribute 'cli'
WARNING:swh.core.cli:Could not load subcommand icinga_plugins: module 'swh.icinga_plugins.cli' has no attribute 'cli'
WARNING:swh.core.cli:Could not load subcommand indexer: module 'swh.indexer.cli' has no attribute 'cli'
fuse: failed to exec fusermount3: No such file or directory
ERROR:root:Error running FUSE: fuse_session_mount failed
$ ls /tmp/foobar
Migrated from T2838 (view on Phabricator)