Throw exception on invalid bucket type (#2642)

Signed-off-by: Emmanuel Ferdman <emmanuelferdman@gmail.com>

Author: emmanuel-ferdman

kafka/metrics/stats/percentiles.py

@@ -30,7 +30,7 @@ def __init__(self, size_in_bytes, bucketing, max_val, min_val=0.0,
  ' to be 0.0.')
  self.bin_scheme = Histogram.LinearBinScheme(self._buckets, max_val)
  else:
- ValueError('Unknown bucket type: %s' % (bucketing,))
+ raise ValueError('Unknown bucket type: %s' % (bucketing,))
 
  def stats(self):
  measurables = []