Support checking unicode TOML

pre_commit_hooks/check_toml.py

diff --git a/pre_commit_hooks/check_toml.py b/pre_commit_hooks/check_toml.py
index 51a1f15..8749675 100644
--- a/pre_commit_hooks/check_toml.py
+++ b/pre_commit_hooks/check_toml.py
@@ -13,8 +13,7 @@
     retval = 0
     for filename in args.filenames:
         try:
-            with open(filename) as f:
-                toml.load(f)
+            toml.load(filename)
         except toml.TomlDecodeError as exc:
             print(f'{filename}: {exc}')
             retval = 1

tests/check_toml_test.py

diff --git a/tests/check_toml_test.py b/tests/check_toml_test.py
index 9f186d1..3283717 100644
--- a/tests/check_toml_test.py
+++ b/tests/check_toml_test.py
@@ -1,7 +1,7 @@
 from pre_commit_hooks.check_toml import main
 
 
-def test_toml_good(tmpdir):
+def test_toml_bad(tmpdir):
     filename = tmpdir.join('f')
     filename.write("""
 key = # INVALID
@@ -12,7 +12,7 @@
     assert ret == 1
 
 
-def test_toml_bad(tmpdir):
+def test_toml_good(tmpdir):
     filename = tmpdir.join('f')
     filename.write(
         """
@@ -27,3 +27,10 @@
     )
     ret = main((filename.strpath,))
     assert ret == 0
+
+
+def test_toml_good_unicode(tmpdir):
+    filename = tmpdir.join('f')
+    filename.write_binary('letter = "\N{SNOWMAN}"\n'.encode())
+    ret = main((filename.strpath,))
+    assert ret == 0