Allow renderers to build with pytype.

PiperOrigin-RevId: 520145182
Change-Id: I7875a1e39d7e65d32132d47a0ff62b4174ea6e16

Author: nimrod-gileadi

dm_control/_render/pyopengl/egl_renderer.py

@@ -96,6 +96,7 @@ class EGLContext(base.ContextBase):
   def __init__(self, max_width, max_height):
     # EGLContext currently only works with `PassthroughRenderExecutor`.
     # TODO(b/110927854) Make this work with the offloading executor.
+    self._context = None
     super().__init__(max_width, max_height, executor.PassthroughRenderExecutor)
 
   def _platform_init(self, unused_max_width, unused_max_height):

dm_control/_render/pyopengl/osmesa_renderer.py

@@ -44,6 +44,10 @@
 class OSMesaContext(base.ContextBase):
   """An OpenGL context backed by OSMesa."""
 
+  def __init__(self, *args, **kwargs):
+    self._context = None
+    super().__init__(*args, **kwargs)
+
   def _platform_init(self, max_width, max_height):
     """Initializes this OSMesa context."""
     self._context = osmesa.OSMesaCreateContextExt(