refactoring: Drop PY2 and PY3 flags

tests/test_build_texinfo.py

@@ -15,10 +15,9 @@ import re
 from subprocess import Popen, PIPE
 
 import pytest
-from six import PY3
 from test_build_html import ENV_WARNINGS
 
-from sphinx.testing.util import remove_unicode_literals, strip_escseq
+from sphinx.testing.util import strip_escseq
 from sphinx.writers.texinfo import TexinfoTranslator
 
 
@@ -30,9 +29,6 @@ TEXINFO_WARNINGS = ENV_WARNINGS + """\
 \\['application/pdf', 'image/svg\\+xml'\\] \\(svgimg.\\*\\)
 """
 
-if PY3:
-    TEXINFO_WARNINGS = remove_unicode_literals(TEXINFO_WARNINGS)
-
 
 @pytest.mark.sphinx('texinfo', testroot='warnings', freshenv=True)
 def test_texinfo_warnings(app, status, warning):