lockfile should silently fail if external lockfile distribution isn't installed

Author: hannes-ucsc

src/bd2k/util/lockfile.py

@@ -3,31 +3,34 @@
 import errno
 import logging as log
 import os
-from lockfile.pidlockfile import PIDLockFile
 
+try:
+    from lockfile.pidlockfile import PIDLockFile
+except:
+    pass
+else:
+    class SmartPIDLockFile( PIDLockFile ):
+        """
+        A PID lock file that breaks the lock if the owning process doesn't exist
+        """
 
-class SmartPIDLockFile( PIDLockFile ):
-    """
-    A PID lock file that breaks the lock if the owning process doesn't exist
-    """
+        def process_alive( self, pid ):
+            try:
+                os.kill( pid, 0 )
+                # now we know the process exists
+                return True
+            except OSError as e:
+                if e.errno == errno.ESRCH:
+                    # now we know the process doesn't exist
+                    return False
+                else:
+                    # now we're not sure
+                    return None
 
-    def process_alive(self, pid):
-        try:
-            os.kill( pid, 0 )
-            # now we know the process exists
-            return True
-        except OSError as e:
-            if e.errno == errno.ESRCH:
-                # now we know the process doesn't exist
-                return False
-            else:
-                # now we're not sure
-                return None
-
-    def acquire(self, timeout=None):
-        owner = self.read_pid( )
-        if owner is not None and owner != os.getpid( ) and self.process_alive( owner ) is False:
-            log.warn( "Breaking lock '%s' since owning process %i is dead."
-                      % ( self.lock_file, owner ) )
-            self.break_lock( )
-        PIDLockFile.acquire( self, timeout )
+        def acquire( self, timeout=None ):
+            owner = self.read_pid( )
+            if owner is not None and owner != os.getpid( ) and self.process_alive( owner ) is False:
+                log.warn( "Breaking lock '%s' since owning process %i is dead."
+                          % (self.lock_file, owner) )
+                self.break_lock( )
+            PIDLockFile.acquire( self, timeout )