Blender Flip Normals

gistfile1.py

import bpy

scene = bpy.context.scene
for ob in scene.objects:
    if ob.type == 'MESH':
        scene.objects.active = ob
        bpy.ops.object.mode_set(mode='EDIT', toggle=False)
        
        # Run an edit-mode operator on every object in the scene [1]
        # [1]: http://blender.stackexchange.com/a/2639/8112
        bpy.ops.mesh.reveal()
        bpy.ops.mesh.select_all(action='SELECT')
        
        # Operation in edit mode
        bpy.ops.mesh.flip_normals()
        
        bpy.ops.object.mode_set(mode='OBJECT', toggle=False)

gistfile2.py

import bpy

scn = bpy.context.scene
sel = bpy.context.selected_objects
meshes = [o for o in sel if o.type == 'MESH']
for obj in meshes:
    scn.objects.active = obj
    bpy.ops.object.editmode_toggle()
    bpy.ops.mesh.select_all(action='SELECT')
    
    # Just flip normals
    bpy.ops.mesh.flip_normals()
    
    bpy.ops.object.mode_set()

Python script fail in gistfile1.py...