rpc: support python 2.6

Fixes #4

splitmount/rpc.py

@@ -23,9 +23,51 @@
 import ctypes.util
 import os
 import subprocess
+import sys
+
+# Monkeypatch subprocess for 2.6
+if sys.version_info[:2] == (2,6):
+    try:
+        from subprocess import STDOUT, check_output, CalledProcessError
+    except ImportError:  # pragma: no cover
+        # python 2.6 doesn't include check_output
+        # monkey patch it in!
+        import subprocess
+        STDOUT = subprocess.STDOUT
+
+        def check_output(*popenargs, **kwargs):
+            if 'stdout' in kwargs:  # pragma: no cover
+                raise ValueError('stdout argument not allowed, '
+                                 'it will be overridden.')
+            process = subprocess.Popen(stdout=subprocess.PIPE,
+                                       *popenargs, **kwargs)
+            output, _ = process.communicate()
+            retcode = process.poll()
+            if retcode:
+                cmd = kwargs.get("args")
+                if cmd is None:
+                    cmd = popenargs[0]
+                raise subprocess.CalledProcessError(retcode, cmd,
+                                                    output=output)
+            return output
+        subprocess.check_output = check_output
+
+        # overwrite CalledProcessError due to `output`
+        # keyword not being available (in 2.6)
+        class CalledProcessError(Exception):
+
+            def __init__(self, returncode, cmd, output=None):
+                self.returncode = returncode
+                self.cmd = cmd
+                self.output = output
+
+            def __str__(self):
+                return "Command '%s' returned non-zero exit status %d" % (
+                    self.cmd, self.returncode)
+        subprocess.CalledProcessError = CalledProcessError
 
 def cli_get_volfile (host, volume):
-    res = subprocess.check_output(["/usr/sbin/gluster","--remote-host={}".format(host),
+    res = subprocess.check_output(["/usr/sbin/gluster","--remote-host={0}".format(host),
         "system","getspec",volume])
     return res
 
@@ -90,5 +132,5 @@ def api_get_volfile (host, volume):
         for line in res.split(u'\n'):
             print(line)
     except:
-        print("bad return value {}".format(res))
+        print("bad return value {0}".format(res))
         raise