Allow Pathlib Path objects to be passed to app.static() helper (#2008)

* Allow Pathlib Path objects to be passed to the app.static file endpoint register helper.

* fixed import sort

* Raise error if static file path is not an accepted object type
Added more tests to improve coverage on the new type checks.

tests/test_static.py

@@ -1,6 +1,6 @@
 import inspect
 import os
-
+from pathlib import Path
 from time import gmtime, strftime
 
 import pytest
@@ -76,6 +76,41 @@ def test_static_file(app, static_file_directory, file_name):
     assert response.body == get_file_content(static_file_directory, file_name)
 
 
+@pytest.mark.parametrize(
+    "file_name",
+    ["test.file", "decode me.txt", "python.png", "symlink", "hard_link"],
+)
+def test_static_file_pathlib(app, static_file_directory, file_name):
+    file_path = Path(get_file_path(static_file_directory, file_name))
+    app.static("/testing.file", file_path)
+    request, response = app.test_client.get("/testing.file")
+    assert response.status == 200
+    assert response.body == get_file_content(static_file_directory, file_name)
+
+
+@pytest.mark.parametrize(
+    "file_name",
+    [b"test.file", b"decode me.txt", b"python.png"],
+)
+def test_static_file_bytes(app, static_file_directory, file_name):
+    bsep = os.path.sep.encode('utf-8')
+    file_path = static_file_directory.encode('utf-8') + bsep + file_name
+    app.static("/testing.file", file_path)
+    request, response = app.test_client.get("/testing.file")
+    assert response.status == 200
+
+
+@pytest.mark.parametrize(
+    "file_name",
+    [dict(), list(), object()],
+)
+def test_static_file_invalid_path(app, static_file_directory, file_name):
+    with pytest.raises(ValueError):
+        app.static("/testing.file", file_name)
+    request, response = app.test_client.get("/testing.file")
+    assert response.status == 404
+
+
 @pytest.mark.parametrize("file_name", ["test.html"])
 def test_static_file_content_type(app, static_file_directory, file_name):
     app.static(