Extract patch and its purpose into a specialized function which can be excluded from coverage.

pkg_resources/__init__.py

@@ -2220,15 +2220,18 @@ register_namespace_handler(object, null_ns_handler)
 
 def normalize_path(filename):
     """Normalize a file/dir name for comparison purposes"""
-    if sys.platform == 'cygwin':
-      # This results in a call to getcwd() if `filename` is relative. Contrary
-      # to POSIX 2008 on Cygwin getcwd (3) contains symlink components. Using
-      # os.path.abspath() works around this limitation. A fix in os.getcwd()
-      # would probably better, in Cygwin even more so except that this seems
-      # to be by design...
-      return os.path.normcase(os.path.realpath(os.path.abspath(filename)))
-    else:
-      return os.path.normcase(os.path.realpath(filename))
+    return os.path.normcase(os.path.realpath(_cygwin_patch(filename)))
+
+
+def _cygwin_patch(filename):  # pragma: nocover
+    """
+    Contrary to POSIX 2008, on Cygwin, getcwd (3) contains
+    symlink components. Using
+    os.path.abspath() works around this limitation. A fix in os.getcwd()
+    would probably better, in Cygwin even more so, except
+    that this seems to be by design...
+    """
+    return os.path.abspath(filename) if sys.platform == 'cygwin' else filename
 
 
 def _normalize_cached(filename, _cache={}):