Use another augmented assignment statement

[elfring]

:eyes: Some source code analysis tools can help to find opportunities for improving software components. :thought_balloon: I propose to increase the usage of augmented assignment statements accordingly.

diff --git a/myfitnesspal/commands.py b/myfitnesspal/commands.py
index e60aed1..91935f3 100644
--- a/myfitnesspal/commands.py
+++ b/myfitnesspal/commands.py
@@ -27,7 +27,7 @@ def get_command_list():
             continue
         message = "{}: {}".format(name, info["description"])
         if info["aliases"]:
-            message = message + "; aliases: {}".format(", ".join(info["aliases"]))
+            message += "; aliases: {}".format(", ".join(info["aliases"]))
         command_lines.append(message)
     prolog = "available commands:\n"
     return prolog + "\n".join(["  " + cmd for cmd in command_lines])