fix trivial 2.6 incompatibility

https://docs.python.org/2/library/stdtypes.html?highlight=decode#str.decode

Changed in version 2.7: Support for keyword arguments added.

Signed-off-by: Pierre Tardy <pierre.tardy@intel.com>

master/buildbot/steps/slave.py

@@ -158,10 +158,10 @@ def commandComplete(self, cmd):
     def getResultSummary(self):
         src = self.src
         if isinstance(src, str):
-            src = src.decode('ascii', errors='replace')
+            src = src.decode('ascii', 'replace')
         dest = self.dest
         if isinstance(dest, str):
-            dest = dest.decode('ascii', errors='replace')
+            dest = dest.decode('ascii', 'replace')
         copy = u"%s to %s" % (src, dest)
         if self.results == SUCCESS:
             rv = u'Copied ' + copy

master/buildbot/util/__init__.py

@@ -313,7 +313,7 @@ def command_to_string(command):
 
     # cmd was a comand and thus probably a bytestring.  Be gentle in
     # trying to covert it.
-    rv = rv.decode('ascii', errors='replace')
+    rv = rv.decode('ascii', 'replace')
 
     return rv