Print more user friendly error when --python version not found

CHANGELOG.md

@@ -3,6 +3,7 @@
 ## 1.4.1
 
 - Set default logging level to WARNING, so debug log messages won't be shown without passing additional flags such as `--verbose`
+- Raise more user friendly error when provided `--python` version is not found.
 
 ## 1.4.0
 

src/pipx/commands/install.py

@@ -1,9 +1,14 @@
 from pathlib import Path
 from typing import List, Optional
 
-from pipx import constants
+from pipx import constants, emojis
 from pipx.commands.common import package_name_from_spec, run_post_install_actions
-from pipx.constants import EXIT_CODE_INSTALL_VENV_EXISTS, EXIT_CODE_OK, ExitCode
+from pipx.constants import (
+    EXIT_CODE_INSTALL_VENV_EXISTS,
+    EXIT_CODE_OK,
+    EXIT_CODE_SPECIFIED_PYTHON_EXECUTABLE_NOT_FOUND,
+    ExitCode,
+)
 from pipx.interpreter import DEFAULT_PYTHON
 from pipx.util import pipx_wrap
 from pipx.venv import Venv, VenvContainer
@@ -102,6 +107,23 @@ def install(
                 include_dependencies,
                 force=force,
             )
+        except FileNotFoundError as e:
+            venv.remove_venv()
+            if python in str(e) or "The system cannot find the file specified" in str(e):
+                print(
+                    pipx_wrap(
+                        f"""
+                           {emojis.hazard} No executable for the provided Python version '{python}' found.
+                           Please make sure the executable name is on your PATH /
+                           the path to the executable is correct.
+                        """,
+                        subsequent_indent=" " * 4,
+                    )
+                )
+                return EXIT_CODE_SPECIFIED_PYTHON_EXECUTABLE_NOT_FOUND
+            else:
+                print()
+                raise
         except (Exception, KeyboardInterrupt):
             print()
             venv.remove_venv()

src/pipx/constants.py

@@ -46,6 +46,7 @@
 EXIT_CODE_UNINSTALL_ERROR = ExitCode(1)
 EXIT_CODE_REINSTALL_VENV_NONEXISTENT = ExitCode(1)
 EXIT_CODE_REINSTALL_INVALID_PYTHON = ExitCode(1)
+EXIT_CODE_SPECIFIED_PYTHON_EXECUTABLE_NOT_FOUND = ExitCode(1)
 
 pipx_log_file: Optional[Path] = None
 

tests/test_install.py

@@ -337,3 +337,9 @@ def test_passed_python_and_force_flag_warning(pipx_temp_env, capsys):
     assert not run_pipx_cli(["install", "pycowsay", "--force"])
     captured = capsys.readouterr()
     assert "--python is ignored when --force is passed." not in captured.out
+
+
+def test_passed_python_not_executable(pipx_temp_env, capsys):
+    assert run_pipx_cli(["install", "--python", "py_not_real", "pycowsay"])
+    captured = capsys.readouterr()
+    assert "No executable for the provided Python version" in captured.out