Python 3 fixes for aksetup.

aksetup_helper.py

@@ -699,7 +699,7 @@ def check_git_submodules():
         stdout_data, _ = popen.communicate()
         if popen.returncode != 0:
             git_error = "git returned error code %d" % popen.returncode
-    except OSError, e:
+    except OSError as e:
         git_error = e
 
     if git_error is not None:
@@ -718,6 +718,7 @@ def check_git_submodules():
 
     popen = Popen(["git", "submodule", "status"], stdout=PIPE)
     stdout_data, _ = popen.communicate()
+    stdout_data = stdout_data.decode("ascii")
     if popen.returncode != 0:
         git_error = "git returned error code %d" % popen.returncode