fix flakey tests

tests/gotosocial/test-script.py

@@ -41,15 +41,34 @@ def run_log(machine: Machine, *commands: str, timeout: int | None = 60) -> str:
 
     return output
 
+@beartype
+def parse_systemd_exec(prop: str) -> str:
+    # idk why, but systemd exec lines are secretly DBus dictionaries,
+    # which `systemctl show -p` represents as an equals-delimited, semicolon-separated,
+    # key-value pair, all in curly braces. e.g.:
+    # { path=/nix/store/… ; argv[]=foobar ; ignore_errors=no ; … }
+    inside = prop.removeprefix('{ ').removesuffix(' }')
+
+    as_dict = dict()
+    for pair in inside.split(';'):
+        k, v = pair.split('=', maxsplit=1)
+        # They have whitespace around the equals but I don't think that's guaranteed.
+        as_dict[k.strip()] = v.strip()
+
+    # If argv is non-empty, use that entirely.
+    if argv := as_dict["argv[]"]:
+        return argv
+    # Otherwise, just use the path, I guess?
+    return as_dict["path"]
+
 @beartype
 def get_config_file() -> str:
     machine.wait_for_unit("gotosocial.service")
-    gotosocial_pid = int(machine.get_unit_property("gotosocial.service", "MainPID"))
-
-    cmdline = machine.succeed(f"cat /proc/{gotosocial_pid}/cmdline")
-    cmdline_args = cmdline.split("\0")
 
+    execstart = machine.get_unit_property("gotosocial.service", "ExecStart")
+    cmdline_args = parse_systemd_exec(execstart).split()
     config_file_idx = cmdline_args.index("--config-path") + 1
+
     config_file = Path(cmdline_args[config_file_idx])
 
     machine.log(f"copying from VM: {config_file=}")