don't choke when loading netcdf string variables

pyglance/glance/io.py

@@ -300,6 +300,12 @@ class nc (object):
         # get our data, save the dtype, and make sure it's a more flexible dtype for now
         variable_object.set_auto_maskandscale(False)  # for now just do the darn calculations ourselves
         temp_input_data = variable_object[:]
+        # if we have a string, just stop now because Glance can't handle strings usefully
+        if isinstance(temp_input_data, str,) :
+            LOG.warning("Variable '" + name + "' has a data type of 'string'. This type of data cannot be "
+                        "analyzed by Glance. This variable will not be analyzed.")
+            raise IONonnumericalTypeError("Variable '" + name + "' is of data type 'string'. "
+                                          "This program can't analyze non-numerical data.")
         LOG.debug("Native input dtype: " + str(temp_input_data.dtype))
         # if this is object data, stop because we can't run our regular analysis on that kind
         if temp_input_data.dtype == object :