Clean up checking for platform and versions when checking for bdist_wininst and

bdist_msi - initial patch supplied by Amaury Forgeot d'Arc.

setup.py

@@ -10,10 +10,15 @@ Unix platforms
 
 import sys
 
-if sys.platform == "win32":
-    if sys.version_info[:2] >= (2, 5):
+import distutils.command
+try:
     import distutils.command.bdist_msi
+except ImportError:
+    distutils.command.bdist_msi = None
+try:
     import distutils.command.bdist_wininst
+except ImportError:
+    distutils.command.bdist_wininst = None
 import distutils.command.bdist_rpm
 import distutils.command.build
 import distutils.dist
@@ -231,9 +236,7 @@ class build(distutils.command.build.build):
 commandClasses = dict(build = build, bdist_rpm = bdist_rpm)
 
 # tweak the Windows installer names to include the Oracle version
-if sys.platform == "win32":
-    
-    if sys.version_info[:2] >= (2, 5):
+if distutils.command.bdist_msi is not None:
 
     class bdist_msi(distutils.command.bdist_msi.bdist_msi):
 
@@ -246,6 +249,8 @@ if sys.platform == "win32":
 
     commandClasses["bdist_msi"] = bdist_msi
 
+if distutils.command.bdist_wininst is not None:
+
     class bdist_wininst(distutils.command.bdist_wininst.bdist_wininst):
 
         def run(self):