Include string_escape encoding in panda3d package, pickle seems to rely on it

direct/src/p3d/panda3d.pdef

@@ -26,7 +26,7 @@ class panda3d(package):
     # These are files that the Panda3D runtime will explicitly look
     # for by name in order to get itself bootstrapped.
     setupPanda3D()
-    
+
     # These are Python modules that are needed by most Panda3D
     # applications.  It doesn't matter too much if we miss one or two
     # here, since any module imported by any of this code will
@@ -57,7 +57,8 @@ class panda3d(package):
     module('panda3d')
 
     # Include various standard Python encodings.  The rest is in morepy.
-    module('encodings', 'encodings.utf_8', 'encodings.ascii')
+    module('encodings', 'encodings.utf_8', 'encodings.ascii',
+           'encodings.string_escape')
 
     # Pick up the shader files that appear in direct/src/filter.
     import direct
@@ -106,7 +107,7 @@ aux-display tinydisplay
 aux-display pandagl
 aux-display tinydisplay
 """
-        
+
     file('Config.prc', extract = True, text = """
 plugin-path $PANDA3D_ROOT
 default-model-extension .bam
@@ -117,7 +118,7 @@ class morepy(package):
     # Additional Python modules provided by the standard Python
     # library.  Include this package to get the full suite of standard
     # Python functionality.
-    
+
     config(display_name = "Python standard library")
     require('panda3d')
 
@@ -196,8 +197,8 @@ class models(package):
     pathname = getModelPath().findFile('cmss12.egg')
     if pathname:
         dir(pathname.getDirname(), newDir = '')
-    
-    
+
+
 class fmod(package):
     # This package includes the FMod audio library.  This is
     # full-featured and robust, but it is closed-source and the
@@ -232,7 +233,7 @@ class audio(package):
     # This package includes the best audio library for the given
     # platform, assuming a non-commercial application.
     require('panda3d')
-    
+
     if platform.startswith('osx'):
         require('fmod')
     else: