[DO NOT MERGE] Try adding Python 2 to Travis.

.travis.yml

@@ -5,6 +5,7 @@ services:
 env:
   # - UBUNTU_VER=14.04 - problems with atari-py
   - UBUNTU_VER=16.04
+  - UBUNTU_VER=16.04.py2
   - UBUNTU_VER=18.04
 
 install: "" # so travis doesn't do pip install requirements.txt

test.dockerfile.16.04.py2

@@ -0,0 +1,47 @@
+# A Dockerfile that sets up a full Gym install with test dependencies
+FROM ubuntu:18.04
+
+# Install keyboard-configuration separately to avoid travis hanging waiting for keyboard selection
+RUN \
+    apt -y update && \
+    apt install -y keyboard-configuration && \
+
+    apt install -y \
+        python-setuptools \
+        python-pip \
+        python-dev \
+        python-pyglet \
+        python-opengl \
+        libjpeg-dev \
+        libboost-all-dev \
+        libsdl2-dev \
+        libosmesa6-dev \
+        patchelf \
+        ffmpeg \
+        xvfb \
+        wget \
+        unzip && \
+
+    apt clean && \
+    rm -rf /var/lib/apt/lists/* && \
+    pip2 install tox && \
+
+# Download mujoco
+    mkdir /root/.mujoco && \
+    cd /root/.mujoco  && \
+    wget https://www.roboti.us/download/mjpro150_linux.zip  && \
+    unzip mjpro150_linux.zip
+
+ARG MUJOCO_KEY
+ENV MUJOCO_KEY=$MUJOCO_KEY
+ENV LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/root/.mujoco/mjpro150/bin
+RUN echo $MUJOCO_KEY | base64 --decode > /root/.mujoco/mjkey.txt
+
+# install dependencies
+COPY . /usr/local/gym/
+RUN cd /usr/local/gym && \
+    tox --notest
+
+WORKDIR /usr/local/gym/
+ENTRYPOINT ["/usr/local/gym/bin/docker_entrypoint"]
+CMD ["tox"]

test.dockerfile.18.04

@@ -6,7 +6,7 @@ RUN \
     apt -y update && \
     apt install -y keyboard-configuration && \
 
-    apt install -y \ 
+    apt install -y \
         python-setuptools \
         python-pip \
         python3-dev \
@@ -40,7 +40,7 @@ RUN echo $MUJOCO_KEY | base64 --decode > /root/.mujoco/mjkey.txt
 # install dependencies
 COPY . /usr/local/gym/
 RUN cd /usr/local/gym && \
-    tox --notest 
+    tox --notest
 
 WORKDIR /usr/local/gym/
 ENTRYPOINT ["/usr/local/gym/bin/docker_entrypoint"]