hghave: improve description of Hypothesis

hghave: improve description of Hypothesis

--- a/tests/hghave.py	Wed Mar 02 21:39:55 2016 +0000
+++ b/tests/hghave.py	Tue Mar 08 14:32:03 2016 +0000
@@ -454,7 +454,7 @@
 def has_slow():
     return os.environ.get('HGTEST_SLOW') == 'slow'
 
-@check("hypothesis", "is Hypothesis installed")
+@check("hypothesis", "Hypothesis automated test generation")
 def has_hypothesis():
     try:
         import hypothesis