only require tokenize_rt for python>=3.8

Author: spyoungtech

setup.py

@@ -19,7 +19,7 @@
     include_package_data=True,
     packages=find_packages("src"),
     package_dir={"": "src"},
-    install_requires=['tokenize_rt'],
+    install_requires=['tokenize_rt; python_version >= "3.8.0"'],
     keywords=["async"],
     python_requires=">=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*, !=3.4.*, <4",
     classifiers=[

src/unasync/__init__.py

@@ -8,9 +8,6 @@
 import os
 import sys
 import tokenize as std_tokenize
-from tokenize_rt import reversed_enumerate
-from tokenize_rt import src_to_tokens
-from tokenize_rt import tokens_to_src
 
 from setuptools.command import build_py as orig
 
@@ -87,6 +84,10 @@ def _unasync_file(self, filepath):
                 print(result, file=f, end="")
 
     def _unasync_remove(self, contents, filename):
+        from tokenize_rt import reversed_enumerate
+        from tokenize_rt import src_to_tokens
+        from tokenize_rt import tokens_to_src
+
         tree = ast.parse(contents, filename=filename)
         tokens = src_to_tokens(contents)
         comment_lines_locations = []