Fix ANSI colors stripped when TERM=dumb or color system undetectable

These patches were developed during Debian rebuild testing with Python 3.13,
where all ANSI sequences were silently stripped even with ALLOW_STYLE=ALWAYS.
The root cause is that Rich's _detect_color_system() returns None when
TERM=dumb, overriding force_terminal=True. Debian build infrastructure always
sets TERM=dumb to prevent interactive terminal usage during builds.

Author: Nilsonfsilva

cmd2/rich_utils.py

@@ -166,8 +166,11 @@ def __init__(
         force_terminal: bool | None = None
         force_interactive: bool | None = None
 
+        color_system: str | None = "auto"
+
         if ALLOW_STYLE == AllowStyle.ALWAYS:
             force_terminal = True
+            color_system = "truecolor"
 
             # Turn off interactive mode if dest is not a terminal which supports it.
             tmp_console = Console(file=file)
@@ -179,6 +182,7 @@ def __init__(
             file=file,
             force_terminal=force_terminal,
             force_interactive=force_interactive,
+            color_system=color_system,
             theme=APP_THEME,
             **kwargs,
         )
@@ -414,6 +418,7 @@ def rich_text_to_string(text: Text) -> str:
 
     console = Console(
         force_terminal=True,
+        color_system="truecolor",
         soft_wrap=True,
         no_color=False,
         theme=APP_THEME,

tests/test_cmd2.py

@@ -3756,6 +3756,9 @@ def test_ansi_terminal_tty(mocker, capsys) -> None:
     app = AnsiApp()
     mocker.patch.object(app.stdout, 'isatty', return_value=True)
     mocker.patch.object(sys.stderr, 'isatty', return_value=True)
+    # Simulate a color-capable terminal: TERMINAL mode respects the TERM env var,
+    # so TERM=dumb would suppress colors even with isatty=True.
+    mocker.patch.dict('os.environ', {'TERM': 'xterm-256color'})
 
     app.onecmd_plus_hooks('echo_error oopsie')
     # if colors are on, the output should have some ANSI style sequences in it