Fix inappropriate use of stdout. Fixes: nasa/fprime#2630 (#198)

Author: LeStarch

src/fprime/fbuild/settings.py

@@ -8,6 +8,7 @@
 """
 import configparser
 import os
+import sys
 from enum import Enum
 from functools import partial
 from pathlib import Path
@@ -172,7 +173,7 @@ def load(settings_file: Path, platform: str = "native", is_ut: bool = False):
             confparse = configparser.ConfigParser()
             confparse.read(settings_file)
         else:
-            print(f"[WARNING] {settings_file} does not exist")
+            print(f"[WARNING] {settings_file} does not exist", file=sys.stderr)
 
         settings = {
             "settings_file": settings_file,