FIX: prevent an infinite loop

closes matplotlib#6057

Author: tacaswell

lib/matplotlib/ticker.py

@@ -1503,6 +1503,7 @@ def __init__(self, base=10.0, subs=[1.0], numdecs=4, numticks=15):
         """
         self.base(base)
         self.subs(subs)
+        # this needs to be validated > 1 with traitlets
         self.numticks = numticks
         self.numdecs = numdecs
 
@@ -1575,6 +1576,9 @@ def tick_values(self, vmin, vmax):
             subs = self._subs
 
         stride = 1
+        if not self.numticks > 1:
+            raise RuntimeError('The number of ticks must be greater than 1 '
+                               'for LogLocator.')
         while numdec / stride + 1 > self.numticks:
             stride += 1