Improve encoding in pkg_resources.tests (#4263)

Author: abravalheri

newsfragments/4263.misc.rst

@@ -0,0 +1 @@
+Avoid implicit ``encoding`` parameter in ``pkg_resources/tests``.

pkg_resources/tests/test_pkg_resources.py

@@ -111,13 +111,13 @@ def test_resource_filename_rewrites_on_change(self):
         filename = zp.get_resource_filename(manager, 'data.dat')
         actual = datetime.datetime.fromtimestamp(os.stat(filename).st_mtime)
         assert actual == self.ref_time
-        f = open(filename, 'w')
+        f = open(filename, 'w', encoding="utf-8")
         f.write('hello, world?')
         f.close()
         ts = self.ref_time.timestamp()
         os.utime(filename, (ts, ts))
         filename = zp.get_resource_filename(manager, 'data.dat')
-        with open(filename) as f:
+        with open(filename, encoding="utf-8") as f:
             assert f.read() == 'hello, world!'
         manager.cleanup_resources()