[gobject-introspection] scanner: document LibtoolImporter.load_module()

[Dieter Verfaillie <dieterv src gnome org>]

commit bb891d97810239fc596ab70503a77a918e5658f5
Author: Dieter Verfaillie <dieterv optionexplicit be>
Date:   Thu Jun 25 17:12:10 2015 +0200

    scanner: document LibtoolImporter.load_module()
    
    It was reported by HeBD on #introspection that Python modules
    use the .pyd extension on windows, not .dll.
    
    The simple fix would have been to just rename to .pyd, but we
    started investigating the possibility of acquiring the suffix tuple(s)
    via imp.get_suffixes() instead. Which led to the discovery that
    imp.load_module() simply ignores the first item of said tuple.
    Thus, there is no use in pretending it to be of any importance
    in this case so we set it to an empty string.
    
    imp_load_module() source for:
    Python 2.6.9 : https://hg.python.org/cpython/file/fcb3ec2842f9/Python/import.c#l3021
    Python 2.7.10: https://hg.python.org/cpython/file/15c95b7d81dc/Python/import.c#l3148
    and just to be future-proof:
    Python 3.4.3 : https://hg.python.org/cpython/file/b4cbecbc0781/Lib/imp.py#l220

 giscanner/libtoolimporter.py |   15 ++++++---------
 1 files changed, 6 insertions(+), 9 deletions(-)
---
diff --git a/giscanner/libtoolimporter.py b/giscanner/libtoolimporter.py
index 0d26b0c..c850103 100644
--- a/giscanner/libtoolimporter.py
+++ b/giscanner/libtoolimporter.py
@@ -20,7 +20,6 @@
 
 import imp
 import os
-import platform
 import sys
 
 from .utils import extract_libtool
@@ -54,16 +53,14 @@ class LibtoolImporter(object):
 
     def load_module(self, name):
         realpath = extract_libtool(self.path)
-        platform_system = platform.system()
 
-        if platform_system == 'Darwin':
-            extension = '.dylib'
-        elif platform_system == 'Windows':
-            extension = '.dll'
-        else:
-            extension = '.so'
+        # The first item of the suffix tuple (which can be, depending on platform,
+        # one or more valid filename extensions used to name c extension modules)
+        # is ignored by imp.load_module(). Thus, there is no use in pretending it
+        # is important and we set it to an empty string.
+        suffix = ('', 'rb', imp.C_EXTENSION)
 
-        mod = imp.load_module(name, open(realpath), realpath, (extension, 'rb', 3))
+        mod = imp.load_module(name, open(realpath), realpath, suffix)
         mod.__loader__ = self
         return mod