Respect a formatter's newline setting when printing

In working on flake8-json, I noticed that setting newline was only
helpful for writing to an ouput-file but not to standard-out. It makes
sense for this setting to apply to both branches otherwise plugins need
to override the method to get the behaviour they expect.

src/flake8/formatting/base.py

@@ -172,7 +172,7 @@ class BaseFormatter(object):
         if self.output_fd is not None:
             self.output_fd.write(output + self.newline)
         if self.output_fd is None or self.options.tee:
-            print(output)
+            print(output, end=self.newline)
 
     def write(self, line, source):
         """Write the line either to the output file or stdout.

tests/unit/test_base_formatter.py

@@ -92,8 +92,8 @@ def test_write_uses_an_output_file(tee):
         if tee:
             assert print_func.called
             assert print_func.mock_calls == [
-                mock.call(line),
-                mock.call(source),
+                mock.call(line, end='\n'),
+                mock.call(source, end='\n'),
             ]
         else:
             assert not print_func.called
@@ -118,8 +118,8 @@ def test_write_uses_print(print_function):
     assert print_function.called is True
     assert print_function.call_count == 2
     assert print_function.mock_calls == [
-        mock.call(line),
-        mock.call(source),
+        mock.call(line, end='\n'),
+        mock.call(source, end='\n'),
     ]