Improve discovery on Windows and provide escape hatchet (#2046)

Signed-off-by: Bernát Gábor <bgabor8@bloomberg.net>

1 files changed, 13 insertions, 6 deletions

diff --git a/src/virtualenv/create/via_global_ref/builtin/cpython/cpython3.py b/src/virtualenv/create/via_global_ref/builtin/cpython/cpython3.py
index 1938509..ad73eed 100644
--- a/src/virtualenv/create/via_global_ref/builtin/cpython/cpython3.py
+++ b/src/virtualenv/create/via_global_ref/builtin/cpython/cpython3.py
@@ -55,20 +55,27 @@ class CPython3Windows(CPythonWindows, CPython3):
     def sources(cls, interpreter):
         for src in super(CPython3Windows, cls).sources(interpreter):
             yield src
-        if not cls.venv_37p(interpreter):
+        if not cls.has_shim(interpreter):
             for src in cls.include_dll_and_pyd(interpreter):
                 yield src
 
-    @staticmethod
-    def venv_37p(interpreter):
-        return interpreter.version_info.minor >= 7
+    @classmethod
+    def has_shim(cls, interpreter):
+        return interpreter.version_info.minor >= 7 and cls.shim(interpreter) is not None
+
+    @classmethod
+    def shim(cls, interpreter):
+        shim = Path(interpreter.system_stdlib) / "venv" / "scripts" / "nt" / "python.exe"
+        if shim.exists():
+            return shim
+        return None
 
     @classmethod
     def host_python(cls, interpreter):
-        if cls.venv_37p(interpreter):
+        if cls.has_shim(interpreter):
             # starting with CPython 3.7 Windows ships with a venvlauncher.exe that avoids the need for dll/pyd copies
             # it also means the wrapper must be copied to avoid bugs such as https://bugs.python.org/issue42013
-            return Path(interpreter.system_stdlib) / "venv" / "scripts" / "nt" / "python.exe"
+            return cls.shim(interpreter)
         return super(CPython3Windows, cls).host_python(interpreter)
 
     @classmethod