Enhanced error message per http://bugs.python.org/setuptools/issue28

(backport from trunk)

--HG--
branch : setuptools-0.6
extra : convert_revision : svn%3A6015fed2-1504-0410-9fe1-9d1591cc4771/sandbox/branches/setuptools-0.6%4065941

setuptools/command/easy_install.py

@@ -639,11 +639,11 @@ Please make the appropriate changes for your system and try again.
             setups = glob(os.path.join(setup_base, '*', 'setup.py'))
             if not setups:
                 raise DistutilsError(
-                    "Couldn't find a setup script in %s" % dist_filename
+                    "Couldn't find a setup script in %s" % os.path.abspath(dist_filename)
                 )
             if len(setups)>1:
                 raise DistutilsError(
-                    "Multiple setup scripts in %s" % dist_filename
+                    "Multiple setup scripts in %s" % os.path.abspath(dist_filename)
                 )
             setup_script = setups[0]