As of pyparsing 2.0.0, Python 2 is no longer supported, so we need to set an upper limit for the range of versions installable by pip

astrofrog · astrofrog · commit 68ee05ed706a · 2013-02-27T13:23:32.000+01:00
diff --git a/setupext.py b/setupext.py
@@ -939,7 +939,7 @@ def get_install_requires(self):
         if sys.version_info[0] >= 3:
             return ['pyparsing>=2.0.0']
         else:
-            return ['pyparsing>=1.5.6']
+            return ['pyparsing>=1.5.6,<=1.5.7']
 
 
 class BackendAgg(OptionalBackendPackage):
