Remove centre setters, add explicit deprecation warning to getters.

i.e. This change makes the deprecated aliases read only, and adds an
explicit warning when reading the values. Previously only got a warning
on setting the value via the deprecated alias.

Bio/Graphics/GenomeDiagram/_AbstractDrawer.py

@@ -433,23 +433,19 @@ def __init__(self, parent, pagesize='A3', orientation='landscape',
         else:
             self.cross_track_links = cross_track_links
 
-    def _set_xcentre(self, value):
-        import warnings
-        import Bio
-        warnings.warn("The _set_xcentre method and .xcentre attribute are deprecated; please use the .xcenter attribute instead", Bio.BiopythonDeprecationWarning)
-        self.xcenter = value
-    xcentre = property(fget = lambda self : self.xcenter,
-                       fset = _set_xcentre,
-                       doc="Backwards compatible alias for xcenter (DEPRECATED)")
-
-    def _set_ycentre(self, value):
-        import warnings
-        import Bio
-        warnings.warn("The _set_ycentre method and .xcentre attribute are deprecated; please use the .ycenter attribute instead", Bio.BiopythonDeprecationWarning)
-        self.ycenter = value
-    ycentre = property(fget = lambda self : self.ycenter,
-                       fset = _set_ycentre,
-                       doc="Backwards compatible alias for ycenter (DEPRECATED)")
+    @property
+    def xcentre(self):
+        """Backwards compatible alias for xcenter (DEPRECATED)"""
+        warnings.warn("The .xcentre attribute is deprecated, use .xcenter instead",
+                      Bio.BiopythonDeprecationWarning)
+        return self.xcenter
+
+    @property
+    def ycentre(self):
+        """Backwards compatible alias for ycenter (DEPRECATED)"""
+        warnings.warn("The .ycentre attribute is deprecated, use .ycenter instead",
+                      Bio.BiopythonDeprecationWarning)
+        return self.ycenter
 
     def set_page_size(self, pagesize, orientation):
         """ set_page_size(self, pagesize, orientation)

Bio/Graphics/GenomeDiagram/_Graph.py

@@ -133,14 +133,12 @@ def __init__(self, id=None, data=None, name=None, style='bar',
         self.linewidth = 2          # linewidth to use in line graphs
         self.center = center        # value at which x-axis crosses y-axis
 
-    def _set_centre(self, value):
-        import warnings
-        import Bio
-        warnings.warn("The _set_centre method and .centre attribute are deprecated; please use the .center attribute instead", Bio.BiopythonDeprecationWarning)
-        self.center = value
-    centre = property(fget = lambda self : self.center,
-                       fset = _set_centre,
-                       doc="Backwards compatible alias for center (DEPRECATED)")
+    @property
+    def centre(self):
+        """Backwards compatible alias for center (DEPRECATED)."""
+        warnings.warn("The .centre attribute is deprecated, use .center instead",
+                      Bio.BiopythonDeprecationWarning)
+        return self.center
 
     def set_data(self, data):
         """ set_data(self, data)