Tolerate non-UTF8 data found in another processes enviroment.

We don't actually care about this data, we only look for our own environment variable and the command line, and we are looking for ASCII stuff we put there anyway, so these replacements are harmless.

Resolves #5518

lutris/util/process.py

@@ -29,7 +29,7 @@ class Process:
     def _read_content(self, file_path):
         """Return the contents from a file in /proc"""
         try:
-            with open(file_path, encoding="utf-8") as proc_file:
+            with open(file_path, encoding="utf-8", errors="replace") as proc_file:
                 content = proc_file.read()
         except PermissionError:
             return ""