analyze_outcomes: keep print_line() method non-static

Signed-off-by: Valerio Setti <valerio.setti@nordicsemi.no>
diff --git a/tests/scripts/analyze_outcomes.py b/tests/scripts/analyze_outcomes.py
index e0c6946..0346404 100755
--- a/tests/scripts/analyze_outcomes.py
+++ b/tests/scripts/analyze_outcomes.py
@@ -23,18 +23,18 @@
         self.warning_count = 0
 
     def info(self, fmt, *args, **kwargs):
-        self.print_line('Info: ' + fmt, *args, **kwargs)
+        self._print_line('Info: ' + fmt, *args, **kwargs)
 
     def error(self, fmt, *args, **kwargs):
         self.error_count += 1
-        self.print_line('Error: ' + fmt, *args, **kwargs)
+        self._print_line('Error: ' + fmt, *args, **kwargs)
 
     def warning(self, fmt, *args, **kwargs):
         self.warning_count += 1
-        self.print_line('Warning: ' + fmt, *args, **kwargs)
+        self._print_line('Warning: ' + fmt, *args, **kwargs)
 
     @staticmethod
-    def print_line(fmt, *args, **kwargs):
+    def _print_line(fmt, *args, **kwargs):
         sys.stderr.write(fmt + '\n', *args, **kwargs)
 
 class TestCaseOutcomes: