Fix Box2D in fresh install (#334)

Before box2d-py 2.3.4, box2d-py works on Linux but breaks on OSX, and
Box2D-kengz works on OSX but breaks on Linux. box2d-py 2.3.4 fixes issue
on OSX and now works on both platforms, and is actively by OpenAI.

See openai/gym#1120.

environment.yml

@@ -15,7 +15,8 @@ dependencies:
         # Please keep alphabetized
         - awscli
         - boto3
-        - Box2D>=2.3.2
+        # box2d-py>=2.3.4 works both on Linux and OSX.
+        - box2d-py>=2.3.4
         - cached_property
         - cloudpickle
         - cma==1.1.06

scripts/setup_linux.sh

@@ -216,10 +216,15 @@ conda activate garage
   fi
 
   # Fix Box2D install
+  # box2d-py 2.3.4 works on both Linux & OSX and is
+  # actively mantained by OpenAI.
+  # Before that, box2d-py works only on Linux,
+  # and Box2D-kengz works only on OSX.
   # See https://github.com/openai/gym/issues/100
   # See https://github.com/pybox2d/pybox2d/issues/82
+  # See https://github.com/openai/gym/pull/1120 (fixed)
   pip uninstall -y Box2D Box2D-kengz box2d-py
-  pip install Box2D
+  pip install box2d-py
 
   # We need a MuJoCo key to import mujoco_py
   cp ${_arg_mjkey} "${HOME}"/.mujoco/mjkey.txt

scripts/setup_osx.sh

@@ -228,10 +228,15 @@ conda activate garage
   pip install -e .
 
   # Fix Box2D install
+  # box2d-py 2.3.4 works on both Linux & OSX and is
+  # actively mantained by OpenAI.
+  # Before that, box2d-py works only on Linux,
+  # and Box2D-kengz works only on OSX.
   # See https://github.com/openai/gym/issues/100
   # See https://github.com/pybox2d/pybox2d/issues/82
+  # See https://github.com/openai/gym/pull/1120 (fixed)
   pip uninstall -y Box2D Box2D-kengz box2d-py
-  pip install Box2D-kengz --no-binary Box2D-kengz
+  pip install box2d-py
 
   # We need a MuJoCo key to import mujoco_py
   cp ${_arg_mjkey} "${HOME}"/.mujoco/mjkey.txt