Fix Job#release and Job#bury when missing YAML

NOTE: Without parsing a Job's stats, we can not automatically preserve
the Job's priority in `release`/`bury`. Unless `release`/`bury` are
passed a priority to use, the Job priority will therefore be reset to
`DEFAULT_PRIORITY`.

beanstalkc.py

@@ -217,6 +217,12 @@ def __init__(self, conn, jid, body, reserved=True):
         self.body = body
         self.reserved = reserved
 
+    def _priority(self):
+        stats = self.stats()
+        if isinstance(stats, dict):
+            return stats['pri']
+        return DEFAULT_PRIORITY
+
     # -- public interface --
 
     def delete(self):
@@ -225,12 +231,12 @@ def delete(self):
 
     def release(self, priority=None, delay=0):
         if self.reserved:
-            self.conn.release(self.jid, priority or self.stats()['pri'], delay)
+            self.conn.release(self.jid, priority or self._priority(), delay)
             self.reserved = False
 
     def bury(self, priority=None):
         if self.reserved:
-            self.conn.bury(self.jid, priority or self.stats()['pri'])
+            self.conn.bury(self.jid, priority or self._priority())
             self.reserved = False
 
     def touch(self):