fix: fsspec closure checks (#1333)

* Fix closed property

* Added closure checks before reading with fsspec

* Fixed error messages

src/uproot/source/fsspec.py

@@ -92,6 +92,9 @@ def chunk(self, start: int, stop: int) -> uproot.source.chunk.Chunk:
         Request a byte range of data from the file as a
         :doc:`uproot.source.chunk.Chunk`.
         """
+        if self.closed:
+            raise OSError(f"file {self._file_path!r} is closed")
+
         self._num_requests += 1
         self._num_requested_chunks += 1
         self._num_requested_bytes += stop - start
@@ -129,6 +132,9 @@ def chunks(
         it is triggered by already-filled chunks, rather than waiting for
         chunks to be filled.
         """
+        if self.closed:
+            raise OSError(f"file {self._file_path!r} is closed")
+
         self._num_requests += 1
         self._num_requested_chunks += len(ranges)
         self._num_requested_bytes += sum(stop - start for start, stop in ranges)
@@ -184,7 +190,7 @@ def closed(self) -> bool:
         True if the associated file/connection/thread pool is closed; False
         otherwise.
         """
-        return False
+        return self._file.closed
 
 
 class FSSpecLoopExecutor(uproot.source.futures.Executor):