feat(nox): support Python 3.10 (#315)

Also install ssh & git to workaround flakiness when using this
as a CircleCI image.

See pydata/pydata-google-auth#43

docker-nox/Dockerfile

@@ -10,6 +10,8 @@ RUN apt-get update -qy && \
     apt-key adv --keyserver keyserver.ubuntu.com --recv-keys F23C5A6CF475977595C89F51BA6932366A755776 && \
     apt-get update -qy && \
     apt-get install -qy \
+        openssh-client \
+        git \
         python2.7 \
         python2.7-dev \
         python3.5 \
@@ -23,6 +25,9 @@ RUN apt-get update -qy && \
         python3.9 \
         python3.9-dev \
         python3.9-distutils \
+        python3.10 \
+        python3.10-dev \
+        python3.10-distutils \
         python3-pip && \
     curl https://bootstrap.pypa.io/pip/2.7/get-pip.py --output /tmp/get-pip.py && \
     python2.7 /tmp/get-pip.py && \
@@ -33,5 +38,6 @@ RUN apt-get update -qy && \
     python3.7 -m pip install --upgrade pip && \
     python3.8 -m pip install --upgrade pip && \
     python3.9 -m pip install --upgrade pip && \
+    python3.10 -m pip install --upgrade pip && \
     python3 -m pip install 'nox==2022.1.7' && \
     rm -rf /var/cache/apt/lists