Keep original indention of Python traceback

changelog.md

@@ -8,6 +8,7 @@ This version is not released yet and is under active development.
 
 - \[pkg\] Add support for `pkg` on FreeBSD.
 - \[choco\] Bump minimal `choco` requirement to `2.0.0`.
+- \[bar-plugin\] Keep original indention of Python traceback.
 - \[mpm\] Build `arm64` binaries on `macos-14`.
 - \[mpm\] Run tests on `macos-14` instead of `macos-13`.
 - \[mpm\] Run tests on Python 3.13-dev branch.

meta_package_manager/bar_plugin.py

@@ -279,13 +279,18 @@ def pp(label: str, *args: str) -> None:
 
         First argument is the menu-line label, separated by a pipe to all other non-
         empty parameters, themselves separated by a space.
+
+        Skip printing of the line if label is empty.
         """
-        print(
-            label.strip(),
-            "|",
-            *(line for line in map(methodcaller("strip"), args) if line),
-            sep=" ",
-        )
+        if label.strip():
+            print(
+                # Do not strip the label to keep character alignements, especially in
+                # table rendering and Python tracebacks.
+                label,
+                "|",
+                *(line for line in map(methodcaller("strip"), args) if line),
+                sep=" ",
+            )
 
     @staticmethod
     def print_error_header() -> None:
@@ -297,12 +302,12 @@ def print_error(self, message: str | Exception, submenu: str = "") -> None:
         """Print a formatted error message line by line.
 
         A red, fixed-width font is used to preserve traceback and exception layout. For
-        compactness, the message is dedented and empty lines are skipped.
+        compactness, the block message is dedented and empty lines are skipped.
 
         Message is always casted to a string as we allow passing of exception objects
         and have them rendered.
         """
-        for line in map(methodcaller("strip"), dedent(str(message)).splitlines()):
+        for line in map(methodcaller("rstrip"), dedent(str(message)).splitlines()):
             if line:
                 self.pp(
                     f"{submenu}{line}",