Get rid of 'sets' module usage under Python 2.4+, so that no warnings

are issued by Python 2.6.  (backport from trunk)

--HG--
branch : setuptools-0.6
extra : convert_revision : svn%3A6015fed2-1504-0410-9fe1-9d1591cc4771/sandbox/branches/setuptools-0.6%4053871

1 files changed, 43 insertions, 2 deletions

diff --git a/pkg_resources.py b/pkg_resources.py
index 4cf81d7b..bfe92e3a 100644
--- a/pkg_resources.py
+++ b/pkg_resources.py
@@ -14,10 +14,31 @@ method.
 """
 
 import sys, os, zipimport, time, re, imp, new
-from sets import ImmutableSet
+
+try:
+    frozenset
+except NameError:
+    from sets import ImmutableSet as frozenset
+
 from os import utime, rename, unlink    # capture these to bypass sandboxing
 from os import open as os_open
 
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 def get_supported_platform():
     """Return this platform's maximum compatible version.
 
@@ -39,6 +60,26 @@ def get_supported_platform():
             pass    # not Mac OS X
     return plat
 
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 __all__ = [
     # Basic resource access and distribution/entry point discovery
     'require', 'run_script', 'get_provider',  'get_distribution',
@@ -2387,7 +2428,7 @@ class Requirement:
         self.index, self.extras = index, tuple(map(safe_extra,extras))
         self.hashCmp = (
             self.key, tuple([(op,parsed) for parsed,trans,op,ver in index]),
-            ImmutableSet(self.extras)
+            frozenset(self.extras)
         )
         self.__hash = hash(self.hashCmp)