[libchamplain] Fix MapProjection attribute error for 'MAP_PROJECTION_MERCATOR'

[Jiří Techet <jiritechet src gnome org>]

commit 4f614845e7f2639138f9fbb24225e6d89da44683
Author: Chris Mayo <aklhfex gmail com>
Date:   Sat Aug 12 11:27:23 2017 +0100

    Fix MapProjection attribute error for 'MAP_PROJECTION_MERCATOR'
    
    https://bugzilla.gnome.org/show_bug.cgi?id=786195

 demos/mapbox.py |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/demos/mapbox.py b/demos/mapbox.py
index d47ee4a..6921ca3 100755
--- a/demos/mapbox.py
+++ b/demos/mapbox.py
@@ -34,7 +34,7 @@ def create_cached_source():
         MIN_ZOOM,
         MAX_ZOOM,
         TILE_SIZE,
-        Champlain.MapProjection.MAP_PROJECTION_MERCATOR,
+        Champlain.MapProjection.MERCATOR,
         "https://a.tiles.mapbox.com/v4/mapbox.streets/#Z#/#X#/#Y#.png?access_token="; + ACCESS_TOKEN,
         Champlain.ImageRenderer())