Patch dlopen() to allow direct paths to all required libs

This is an update of the patch submitted in
https://github.com/NixOS/nixpkgs/commit/b13e44e094989d3a902f8c73b22e8d3c0cc7acf4
by Alexander V. Nikolaev <avn@avnik.info>

---
 cairocffi/__init__.py | 34 ++++++++++++++++------------------
 1 file changed, 16 insertions(+), 18 deletions(-)

diff --git a/cairocffi/__init__.py b/cairocffi/__init__.py
index 307d58c..43c29e3 100644
--- a/cairocffi/__init__.py
+++ b/cairocffi/__init__.py
@@ -21,28 +21,26 @@ VERSION = __version__ = (Path(__file__).parent / 'VERSION').read_text().strip()
 version = '1.17.2'
 version_info = (1, 17, 2)

+# Use hardcoded soname, because ctypes.util use gcc/objdump which shouldn't be
+# required for runtime
+_LIBS = {
+    'cairo': '@cairo@/lib/libcairo@ext@',
+    'glib-2.0': '@glib@/lib/libglib-2.0@ext@',
+    'gobject-2.0': '@glib@/lib/libgobject-2.0@ext@',
+    'gdk_pixbuf-2.0': '@gdk_pixbuf@/lib/libgdk_pixbuf-2.0@ext@',
+}
+

 def dlopen(ffi, library_names, filenames):
     """Try various names for the same library, for different platforms."""
-    exceptions = []
-
     for library_name in library_names:
-        library_filename = find_library(library_name)
-        if library_filename:
-            filenames = (library_filename,) + filenames
-        else:
-            exceptions.append(
-                'no library called "{}" was found'.format(library_name))
-
-    for filename in filenames:
-        try:
-            return ffi.dlopen(filename)
-        except OSError as exception:  # pragma: no cover
-            exceptions.append(exception)
-
-    error_message = '\n'.join(  # pragma: no cover
-        str(exception) for exception in exceptions)
-    raise OSError(error_message)  # pragma: no cover
+        path = _LIBS.get(library_name, None)
+        if path:
+            lib = ffi.dlopen(path)
+            if lib:
+                return lib
+
+    raise OSError("dlopen() failed to load a library: %s as %s" % (library_name, path))


 cairo = dlopen(
--
2.19.2