Backport v2 privilege elevation logic to v1 (#260)

* Backport v2 handling of privilege elevation to v1 legacy code

* Add news file

* Only use .nonadmin files for privilege elevation logic

* Ensure that .nonadmin files do not exists before asking for privilege elevation

menuinst/_legacy/__init__.py

@@ -14,7 +14,7 @@
 except ImportError:
     __version__ = "dev"
 
-from ..utils import DEFAULT_BASE_PREFIX, DEFAULT_PREFIX
+from ..utils import DEFAULT_BASE_PREFIX, DEFAULT_PREFIX, python_executable
 
 if sys.platform == 'win32':
     from ..platforms.win_utils.win_elevate import isUserAdmin, runAsAdmin
@@ -59,9 +59,7 @@ def install(path, remove=False, prefix=None, recursing=False, root_prefix=None):
     if not sys.platform == 'win32':
         raise RuntimeError("menuinst._legacy is only supported on Windows.")
 
-    # this root_prefix is intentional.  We want to reflect the state of the root installation.
-
-    if not exists(join(root_prefix, '.nonadmin')):
+    if not exists(join(prefix, ".nonadmin")) and not exists(join(root_prefix, ".nonadmin")):
         if isUserAdmin():
             _install(path, remove, prefix, mode='system', root_prefix=root_prefix)
         else:
@@ -70,7 +68,7 @@ def install(path, remove=False, prefix=None, recursing=False, root_prefix=None):
                 if not recursing:
                     retcode = runAsAdmin(
                         [
-                            join(root_prefix, 'python'),
+                            *python_executable(),
                             '-c',
                             "import menuinst; menuinst.install(%r, %r, %r, %r, %r)"
                             % (path, bool(remove), prefix, True, root_prefix),

news/260-backport-v2-admin-to-v1

@@ -0,0 +1,19 @@
+### Enhancements
+
+* Partially backport privilege elevation logic from v2 to v1. (#260)
+
+### Bug fixes
+
+* <news item>
+
+### Deprecations
+
+* <news item>
+
+### Docs
+
+* <news item>
+
+### Other
+
+* <news item>