Fix to pass Eunit tests with Erlang/OTP 26

In Erlang 25 and older an unknown error message is formatted like this:

  1> file:format_error(unexpected).
  "unknown POSIX error"

However since Erlang 26 the result is different:

  1> file:format_error(unexpected).
  "unknown POSIX error: unexpected"

Let's add another case to handle both variants.

Signed-off-by: Peter Lemenkov <[email protected]>

src/p1_file_queue.erl

@@ -200,7 +200,9 @@ format_error({not_owner, Path}) ->
  "not a file queue owner (" ++ binary_to_list(Path) ++ ")";
 format_error({Posix, Path}) ->
  case file:format_error(Posix) of
- "unknown POSIX error" ->
+ "unknown POSIX error" -> % Erlang/OTP 25 and older
+ atom_to_list(Posix) ++ " (" ++ binary_to_list(Path) ++ ")";
+ [$u, $n, $k, $n, $o, $w, $n | _] -> % Erlang/OTP 26 and newer
  atom_to_list(Posix) ++ " (" ++ binary_to_list(Path) ++ ")";
  Reason ->
  Reason ++ " (" ++ binary_to_list(Path) ++ ")"