uninstall: use polkit on PermissionError

As for an install, the uninstall should be able
to use the polkit to gain privileges.

mesonbuild/scripts/uninstall.py

@@ -14,8 +14,16 @@
 
 import os
 import typing as T
+import shutil
+import sys
+try:
+    from __main__ import __file__ as main_file
+except ImportError:
+    # Happens when running as meson.exe which is native Windows.
+    # This is only used for pkexec which is not, so this is fine.
+    main_file = None
 
-logfile = 'meson-logs/install-log.txt'
+INSTALL_LOGFILE = 'meson-logs/install-log.txt'
 
 def do_uninstall(log: str) -> None:
     failures = 0
@@ -32,17 +40,26 @@ def do_uninstall(log: str) -> None:
             print('Deleted:', fname)
             successes += 1
         except Exception as e:
-            print(f'Could not delete {fname}: {e}.')
-            failures += 1
+            if e.__class__ == PermissionError  and shutil.which('pkexec') is not None and 'PKEXEC_UID' not in os.environ:
+                print('Installation failed due to insufficient permissions.')
+                print('Attempting to use polkit to gain elevated privileges...')
+                os.execlp('pkexec', 'pkexec', sys.executable, main_file, *sys.argv[1:], os.getcwd())
+            else:
+                print(f'Could not delete {fname}: {e}.')
+                failures += 1
     print('\nUninstall finished.\n')
     print('Deleted:', successes)
     print('Failed:', failures)
     print('\nRemember that files created by custom scripts have not been removed.')
 
 def run(args: T.List[str]) -> int:
+    logfile = INSTALL_LOGFILE
     if args:
-        print('Weird error.')
-        return 1
+        if os.path.isdir(args[0]):
+            logfile = os.path.join(args[0],logfile)
+        else:
+            print(f'{args[0]} should be a path')
+            return 1
     if not os.path.exists(logfile):
         print('Log file does not exist, no installation has been done.')
         return 0