use shutil.which when finding a suitable python

src/poetry/utils/env.py

@@ -970,10 +970,14 @@ def create_venv(
                 ):
                     continue
 
-                python = "python" + python_to_try
-
                 if self._io.is_debug():
-                    self._io.write_error_line(f"<debug>Trying {python}</debug>")
+                    self._io.write_error_line(
+                        f"<debug>Trying python{python_to_try}</debug>"
+                    )
+
+                python = shutil.which(f"python{python_to_try}")
+                if python is None:
+                    continue
 
                 try:
                     python_patch = decode(
@@ -985,9 +989,6 @@ def create_venv(
                 except CalledProcessError:
                     continue
 
-                if not python_patch:
-                    continue
-
                 if supported_python.allows(Version.parse(python_patch)):
                     self._io.write_error_line(
                         f"Using <c1>{python}</c1> ({python_patch})"

tests/utils/test_env.py

@@ -197,7 +197,8 @@ def check_output(cmd: list[str], *args: Any, **kwargs: Any) -> str:
         elif "sys.version_info[:2]" in python_cmd:
             return f"{version.major}.{version.minor}"
         elif "import sys; print(sys.executable)" in python_cmd:
-            return f"/usr/bin/{cmd[0]}"
+            basename = os.path.basename(cmd[0])
+            return f"/usr/bin/{basename}"
         else:
             assert "import sys; print(sys.prefix)" in python_cmd
             return str(Path("/prefix"))
@@ -1070,6 +1071,7 @@ def test_create_venv_tries_to_find_a_compatible_python_executable_using_generic_
     poetry.package.python_versions = "^3.6"
 
     mocker.patch("sys.version_info", (2, 7, 16))
+    mocker.patch("shutil.which", side_effect=lambda py: f"/usr/bin/{py}")
     mocker.patch(
         "subprocess.check_output",
         side_effect=check_output_wrapper(Version.parse("3.7.5")),
@@ -1107,6 +1109,7 @@ def test_create_venv_tries_to_find_a_compatible_python_executable_using_specific
     poetry.package.python_versions = "^3.6"
 
     mocker.patch("sys.version_info", (2, 7, 16))
+    mocker.patch("shutil.which", side_effect=lambda py: f"/usr/bin/{py}")
     mocker.patch(
         "subprocess.check_output", side_effect=["3.5.3", "3.9.0", "/usr/bin/python3.9"]
     )
@@ -1546,13 +1549,14 @@ def test_create_venv_accepts_fallback_version_w_nonzero_patchlevel(
 
     def mock_check_output(cmd: str, *args: Any, **kwargs: Any) -> str:
         if GET_PYTHON_VERSION_ONELINER in cmd:
-            if "python3.5" in cmd:
+            if "python3.5" in cmd[0]:
                 return "3.5.12"
             else:
                 return "3.7.1"
         else:
             return "/usr/bin/python3.5"
 
+    mocker.patch("shutil.which", side_effect=lambda py: f"/usr/bin/{py}")
     check_output = mocker.patch(
         "subprocess.check_output",
         side_effect=mock_check_output,
@@ -1662,6 +1666,7 @@ def test_create_venv_project_name_empty_sets_correct_prompt(
     venv_name = manager.generate_env_name("", str(poetry.file.parent))
 
     mocker.patch("sys.version_info", (2, 7, 16))
+    mocker.patch("shutil.which", side_effect=lambda py: f"/usr/bin/{py}")
     mocker.patch(
         "subprocess.check_output",
         side_effect=check_output_wrapper(Version.parse("3.7.5")),