cqlsh: Fix display of -infinity

Patch by Adam Holmberg; reviewed by Tyler Hobbs for CASSANDRA-10523

CHANGES.txt

@@ -1,4 +1,5 @@
 2.1.12
+ * (cqlsh) Distinguish negative and positive infinity in output (CASSANDRA-10523)
  * (cqlsh) allow custom time_format for COPY TO (CASSANDRA-8970)
  * Don't allow startup if the node's rack has changed (CASSANDRA-10242)
  * (cqlsh) show partial trace if incomplete after max_trace_wait (CASSANDRA-7645)

pylib/cqlshlib/formatting.py

@@ -156,7 +156,7 @@ def format_floating_point_type(val, colormap, float_precision, **_):
     if math.isnan(val):
         bval = 'NaN'
     elif math.isinf(val):
-        bval = 'Infinity'
+        bval = 'Infinity' if val > 0 else '-Infinity'
     else:
         exponent = int(math.log10(abs(val))) if abs(val) > sys.float_info.epsilon else -sys.maxint - 1
         if -4 <= exponent < float_precision: