Use a backport for check_output that is not part of python 2.6

lib/galaxy/web/base/interactive_environments.py

@@ -5,7 +5,8 @@ import json
 import stat
 import random
 import tempfile
-from subprocess import Popen, PIPE, check_output
+import subprocess
+from subprocess import Popen, PIPE
 
 from galaxy.util.bunch import Bunch
 from galaxy import web
@@ -16,6 +17,32 @@ import logging
 log = logging.getLogger(__name__)
 
 
+# Python 2.6 does not support the check_output command.
+# As a workaround we use a backport from https://gist.github.com/edufelipe/1027906
+# until we do not support Python 2.6 anymore.
+
+if "check_output" not in dir( subprocess ):
+    def check_output(*popenargs, **kwargs):
+        r"""Run command with arguments and return its output as a byte string.
+        Backported from Python 2.7 as it's implemented as pure python on stdlib.
+        >>> check_output(['/usr/bin/python', '--version'])
+        Python 2.6.2
+        """
+        process = subprocess.Popen(stdout=subprocess.PIPE, *popenargs, **kwargs)
+        output, unused_err = process.communicate()
+        retcode = process.poll()
+        if retcode:
+            cmd = kwargs.get("args")
+            if cmd is None:
+                cmd = popenargs[0]
+            error = subprocess.CalledProcessError(retcode, cmd)
+            error.output = output
+            raise error
+        return output
+else:
+    from subprocess import check_output
+
+
 class InteractiveEnviornmentRequest(object):
 
     def __init__(self, trans, plugin):