Raise NoWorkFound when a quanta cant be run

Some quanta cant run because they don't have enough data to do
statistics on. Raise a NoWorkFound error so the execution
framework does not register this as a pipeline execution failure.

python/lsst/analysis/drp/skyPlot.py

@@ -1,3 +1,4 @@
+from multiprocessing.sharedctypes import Value
 import matplotlib.pyplot as plt
 import numpy as np
 from scipy.stats import median_absolute_deviation as sigmaMad
@@ -388,8 +389,16 @@ def skyPlot(self, catPlot, plotInfo, sumStats):
             nBins = 45
             xBinEdges = np.linspace(minRa, maxRa, nBins + 1)
             yBinEdges = np.linspace(minDec, maxDec, nBins + 1)
-            binnedStats, xEdges, yEdges, binNums = binned_statistic_2d(xs, ys, colorVals, statistic="median",
-                                                                       bins=(xBinEdges, yBinEdges))
+            try:
+                binnedStats, xEdges, yEdges, binNums = binned_statistic_2d(xs, ys, colorVals,
+                                                                           statistic="median",
+                                                                           bins=(xBinEdges, yBinEdges))
+            except ValueError as err:
+                # This is raised with the following message:
+                # ValueError: The smallest edge difference is numerically 0.
+                # and means this data cannot be processed as there is no
+                # appropriate data to process.
+                raise pipeBase.NoWorkFound() from err
 
             if len(xs) > 5000:
                 s = 500/(len(xs)**0.5)