[entropy.client.misc, entropy.output] fixes for Python 3

ConfigurationFiles._load_maybe_add (equo.client.misc): path is in bytes here

_std_write (entropy.output): fixes crash in equo conf update with "Replace
original with update" when there is an error in which case msg can be bytes:

  File ".../entropy/lib/entropy/tools.py", line 687, in movefile
    print_generic("!!! Failed to move", src, "to", dest)
  File ".../entropy/lib/entropy/output.py", line 596, in print_generic
    _std_write(msg, stderr = stderr)
  File ".../entropy/lib/entropy/output.py", line 493, in _std_write
    obj.write(msg)

lib/entropy/client/misc.py

@@ -251,7 +251,8 @@ class ConfigurationFiles(dict):
                 self._entropy.output(
                     darkred("%s: %s") % (
                         _("Automerging file"),
-                        darkgreen(filepath),
+                        darkgreen(
+                            self._unicode_path(filepath)),
                         ),
                     importance = 0,
                     level = "info"

lib/entropy/output.py

@@ -489,6 +489,12 @@ def _std_write(msg, stderr = False):
     if stderr:
         obj = sys.stderr
 
+    if const_is_python3() and not const_isunicode(msg):
+        obj.flush()
+        obj.buffer.write(msg)
+        obj.flush()
+        return
+
     try:
         obj.write(msg)
     except UnicodeEncodeError: