entropy.transceivers.urlFetcher: always close file objects on disk

when reusing urlFetcher class more than once, make sure we close
every opened local file

libraries/entropy/transceivers.py

@@ -53,6 +53,7 @@ class urlFetcher:
         self.__disallow_redirect = disallow_redirect
         self.__speedlimit = speed_limit # kbytes/sec
         self.__existed_before = False
+        self.localfile = None
 
         # important to have this here too
         self.__datatransfer = 0
@@ -104,6 +105,16 @@ class urlFetcher:
 
     def __setup_resume_support(self):
 
+        # if client uses this instance more than
+        # once, make sure we close previously opened
+        # files.
+        if isinstance(self.localfile, file):
+            try:
+                self.localfile.flush()
+                self.localfile.close()
+            except (IOError, OSError,):
+                pass
+
         # resume support
         if os.path.isfile(self.__path_to_save) and \
             os.access(self.__path_to_save,os.W_OK) and self.__resume: