print an explanation when setup.py fails due to the MSSDK not being found

Author: mhammond

setup.py

@@ -316,7 +316,14 @@ def monkeypatched_link(self, target_desc, objects, output_filename, *args, **kw)
 
 sdk_dir = find_platform_sdk_dir()
 if not sdk_dir:
-    raise RuntimeError("Can't find the Windows SDK")
+  print
+  print "It looks like you are trying to build pywin32 in an environment without"
+  print "the necessary tools installed. It's much easier to grab binaries!"
+  print
+  print "Please read the docstring at the top of this file, or read README.md"
+  print "for more information."
+  print
+  raise RuntimeError("Can't find the Windows SDK")
 
 class WinExt (Extension):
     # Base class for all win32 extensions, with some predefined