watchman: ignore some of watchman errors

Don't display 'illegal_fstypes' errors. In environments with network
filesystems, the error messages are quickly pilling up and polluting outputs.

Differential Revision: https://phab.mercurial-scm.org/D5955

hgext/fsmonitor/__init__.py

@@ -180,6 +180,7 b' def _handleunavailable(ui, state, ex):'
     if isinstance(ex, watchmanclient.Unavailable):
         # experimental config: fsmonitor.verbose
         if ex.warn and ui.configbool('fsmonitor', 'verbose'):
+            if 'illegal_fstypes' not in str(ex):
             ui.warn(str(ex) + '\n')
         if ex.invalidate:
             state.invalidate()