Replace unencodable characters in stdout

spin/__main__.py

@@ -1,6 +1,7 @@
 import collections
 import importlib
 import importlib.util
+import io
 import os
 import pathlib
 import sys
@@ -42,6 +43,10 @@ def _detect_config_dir(path: pathlib.Path) -> pathlib.Path | None:
 
 
 def main():
+    # Replace characters, such as emoji, that the stdout encoding cannot represent
+    if isinstance(sys.stdout, io.TextIOWrapper):
+        sys.stdout.reconfigure(errors="replace")
+
     # Alias `spin help` to `spin --help`
     if (len(sys.argv) == 2) and (sys.argv[1] == "help"):
         sys.argv[1] = "--help"

spin/tests/test_build_cmds.py

@@ -201,3 +201,12 @@ def test_parallel_builds(example_pkg):
     assert "build-install" in example_pkg_path
     assert "parallel/build-install" in example_pkg_parallel_path
     assert "parallel/build-install" not in example_pkg_path
+
+
+@skip_py_lt_311  # python command does not run on older pythons
+def test_unencodable_output(example_pkg):
+    # `spin python` prints an emoji, which ASCII cannot encode
+    p = spin(
+        "python", "--", "-c", "pass", env={**os.environ, "PYTHONIOENCODING": "ascii"}
+    )
+    assert p.returncode == 0