Improved responsiveness when setting windows title and printing alerts

Author: kmvanbrunt

CHANGELOG.md

@@ -1,3 +1,8 @@
+## 0.9.24 (TBD, 2020)
+* Enhancements
+    * Flushing stderr when setting the window title and printing alerts for better responsiveness in cases where
+    stderr is not unbuffered.
+
 ## 0.9.23 (January 9, 2020)
 * Bug Fixes
     * Fixed bug where startup script containing a single quote in its file name was incorrectly quoted

cmd2/cmd2.py

@@ -3802,6 +3802,7 @@ def async_alert(self, alert_msg: str, new_prompt: Optional[str] = None) -> None:
                                                     cursor_offset=rl_get_point(), alert_msg=alert_msg)
                 if rl_type == RlType.GNU:
                     sys.stderr.write(terminal_str)
+                    sys.stderr.flush()
                 elif rl_type == RlType.PYREADLINE:
                     # noinspection PyUnresolvedReferences
                     readline.rl.mode.console.write(terminal_str)
@@ -3854,6 +3855,7 @@ def set_window_title(self, title: str) -> None:  # pragma: no cover
         if self.terminal_lock.acquire(blocking=False):
             try:
                 sys.stderr.write(ansi.set_title_str(title))
+                sys.stderr.flush()
             except AttributeError:
                 # Debugging in Pycharm has issues with setting terminal title
                 pass