unknown setuptools version can be added in the working set, refs #90

--HG--
branch : distribute
extra : rebase_source : c0aabd45025465b61ffd23a2196994f4afece233

1 files changed, 5 insertions, 1 deletions

diff --git a/pkg_resources.py b/pkg_resources.py
index 31d83554..96381932 100644
--- a/pkg_resources.py
+++ b/pkg_resources.py
@@ -2253,7 +2253,11 @@ class Distribution(object):
         loc = loc or self.location
 
         if self.project_name == 'setuptools':
-            if '0.7' in self.version:
+            try:
+                version = self.version
+            except ValueError:
+                version = ''
+            if '0.7' in version:
                 raise ValueError(
                     "A 0.7-series setuptools cannot be installed "
                     "with distribute")