Fix use of getheaders on Python 3

setuptools/package_index.py

@@ -13,6 +13,7 @@ except ImportError:
     from md5 import md5
 from fnmatch import translate
 from .py24compat import wraps
+from setuptools.py27compat import get_all_headers
 
 EGG_FRAGMENT = re.compile(r'^egg=([-A-Za-z0-9_.]+)$')
 HREF = re.compile("""href\\s*=\\s*['"]?([^'"> ]+)""", re.I)
@@ -608,10 +609,8 @@ class PackageIndex(Environment):
             size = -1
             if "content-length" in headers:
                 # Some servers return multiple Content-Length headers :(
-                if not hasattr(headers, 'get_all'):
-                    # Older versions of Python don't have the get_all method
-                    headers.get_all = headers.getheaders
-                size = max(map(int,headers.get_all("Content-Length")))
+                sizes = get_all_headers(headers, 'Content-Length')
+                size = max(map(int, sizes))
                 self.reporthook(url, filename, blocknum, bs, size)
             tfp = open(filename,'wb')
             while True:

setuptools/py27compat.py

+"""
+Compatibility Support for Python 2.7 and earlier
+"""
+
+import sys
+
+def get_all_headers(message, key):
+	"""
+	Given an HTTPMessage, return all headers matching a given key.
+	"""
+	return message.get_all(key)
+
+if sys.version_info < (3,):
+	def get_all_headers(message, key):
+		return message.getheaders(key)