Fix commandline test character encoding issues for Py3

tests/test_cmdline.py

@@ -54,11 +54,6 @@ def setup_module():
 def teardown_module():
     server_stop()
 
-# Add an encoding property to StringIO so Python will convert Unicode
-# properly when writing or reading.
-class UTF8StringIO(io.StringIO):
-    encoding = 'utf-8'
-
 class TestCmdline(object):
 
     def run(self, arg_string, infile=None, outfile=None):
@@ -76,22 +71,20 @@ class TestCmdline(object):
                 ( sys.stdin, sys.stdout, sys.stderr ) = self.saved
         # Empty input if none provided
         if infile is None:
-            infile = UTF8StringIO("")
+            infile = io.StringIO("")
         # Capture stderr
-        errfile = UTF8StringIO()
+        errfile = io.StringIO()
         if outfile is None:
             # If no output file, capture stdout with stderr
             outfile = errfile
         with stdio_wrapper(infile, outfile, errfile) as s:
             try:
-                # shlex doesn't support Unicode very well.  Encode the
-                # string as UTF-8 explicitly before splitting.
-                args = shlex.split(arg_string.encode('utf-8'))
+                args = shlex.split(arg_string)
                 nilmdb.cmdline.Cmdline(args).run()
                 sys.exit(0)
             except SystemExit as e:
                 exitcode = e.code
-        captured = nilmdb.utils.str.decode(outfile.getvalue())
+        captured = outfile.getvalue()
         self.captured = captured
         self.exitcode = exitcode