Merge pull request #1165 from kesslerm/fix/python-plugin-crash

Fix occasional crashes in python plugins

diff --cc python.d/python_modules/base.py
index 87364c02706dfe3aa57506d83e3d28c1fc1d4ce4,cb04274b8579edf57847e0668dd46d03a7c1382d..201128f876fec33a9d89c6f0ae4de73ed8c2b4ab
--- 1/python.d/python_modules/base.py
--- 2/python.d/python_modules/base.py
+++ b/python.d/python_modules/base.py
@@@ -164,11 -160,10 +164,11 @@@ class SimpleService(threading.Thread)
              try:
                  status = self._run_once()
              except Exception as e:
 -                self.error("Something wrong: ", str(e))
 +                self.alert("internal error - aborting data collection: " + str(e))
                  return
 +
              if status:  # handle retries if update failed
-                 time.sleep(self.timetable['next'] - time.time())
+                 time.sleep(max (0, self.timetable['next'] - time.time()))
                  self.retries_left = self.retries
              else:
                  self.retries_left -= 1