Catch errors when unmounting snapshots

lvmsnapshot.py

@@ -264,12 +264,15 @@ class Snapshot:
 
     def remove(self):
         logging.debug("removing snapshot {}".format(self.get_name()))
+        try:
             self.unmount()
             remove_command = [
                 "/sbin/lvremove",
                 self.get_full_volume()
             ]
             run_process(remove_command, check=True)
+        except sp.CalledProcessError:
+            logging.warn("Removing {} failed".format(self.get_name()))
 
     def unmount(self):
         logging.debug("unmounting snapshot {}".format(self.get_name()))