Add PYTHON and python2/python3 support

Perhaps we should have an option for py2/p3, but for
now we detect the default python version and it can
also be specified via the PYTHON env var.

util/install.sh

@@ -102,6 +102,14 @@ function version_ge {
     [ "$1" == "$latest" ]
 }
 
+# Attempt to identify Python version
+PYTHON=${PYTHON:-python}
+if $PYTHON --version |& grep 'Python 2' > /dev/null; then
+    PYTHON_VERSION=2; PYPKG=python
+else
+    PYTHON_VERSION=3; PYPKG=python3
+fi
+echo "${PYTHON} is version ${PYTHON_VERSION}"
 
 # Kernel Deb pkg to be removed:
 KERNEL_IMAGE_OLD=linux-image-2.6.26-33-generic
@@ -145,19 +153,19 @@ function mn_deps {
         $install gcc make socat psmisc xterm openssh-clients iperf \
             iproute telnet python-setuptools libcgroup-tools \
             ethtool help2man pyflakes pylint python-pep8 python-pexpect
-	elif [ "$DIST" = "SUSE LINUX"  ]; then
+    elif [ "$DIST" = "SUSE LINUX"  ]; then
 		$install gcc make socat psmisc xterm openssh iperf \
-			iproute telnet python-setuptools libcgroup-tools \
-			ethtool help2man python-pyflakes python3-pylint python-pep8 python-pexpect
-    else
+			iproute telnet ${PYPKG}-setuptools libcgroup-tools \
+			ethtool help2man python-pyflakes python3-pylint python-pep8 ${PYPKG}-pexpect
+    else  # Debian/Ubuntu
         $install gcc make socat psmisc xterm ssh iperf iproute2 telnet \
-            python-setuptools cgroup-bin ethtool help2man \
-            pyflakes pylint pep8 python-pexpect
+                 cgroup-bin ethtool help2man pyflakes pylint pep8 \
+                 ${PYPKG}-setuptools ${PYPKG}-pexpect
     fi
 
     echo "Installing Mininet core"
     pushd $MININET_DIR/mininet
-    sudo make install
+    sudo PYTHON=${PYTHON} make install
     popd
 }