Add per-platform logic to define path to CONFIG_DIR

Use platform module from Python standard library to define the
path to the appropriate location for user configuration files, with
fallback to former default path.

soco_cli/aliases.py

@@ -2,10 +2,19 @@
 
 import logging
 import pickle
-from os import mkdir, path
+import platform
+from os import environ, mkdir, path
 from typing import List, Tuple, Union
 
-CONFIG_DIR = path.join(path.expanduser("~"), ".soco-cli")
+if platform.system() == "Linux":
+    if "XDG_CONFIG_HOME" in environ:
+        CONFIG_DIR = path.join(path.expandvars("${XDG_CONFIG_HOME}"), "soco-cli")
+    else:
+        CONFIG_DIR = path.join(path.expanduser("~user"), ".config", "soco-cli")
+elif platform.system() == "Windows":
+    CONFIG_DIR = path.join(path.expandvars("%LOCALAPPDATA%"), "soco-cli")
+else:
+    CONFIG_DIR = path.join(path.expanduser("~user"), ".soco-cli")
 ALIAS_FILE = path.join(CONFIG_DIR, "aliases.pickle")
 
 
@@ -45,13 +54,19 @@ def remove_alias(self, alias_name: str) -> bool:
     def alias_names(self) -> List[str]:
         return list(self._aliases.keys())
 
+    def _confirm_config_dir() -> bool:
+    if not path.exists(CONFIG_DIR):
+        logging.info("Creating directory '{}'".format(SOCO_CLI_DIR))
+        try:
+            mkdir(CONFIG_DIR)
+            return True
+        except:
+            error_report("Failed to create directory '{}'".format(CONFIG_DIR))
+            return False
+
     def save_aliases(self) -> None:
-        if not path.exists(CONFIG_DIR):
-            try:
-                logging.info("Creating directory '{}'".format(CONFIG_DIR))
-                mkdir(CONFIG_DIR)
-            except:
-                pass
+        if not _confirm_config_dir():
+            pass
         with open(ALIAS_FILE, "wb") as f:
             logging.info("Saving aliases")
             pickle.dump(self._aliases, f)