Fixing issue on py38

AttributeError: type object 'Callable' has no attribute '_abc_registry'

Author: awais786

.travis.yml

@@ -20,11 +20,12 @@ matrix:
     - name: "Lint"
       python: "3.7"
       env: TOXENV=lint
+    - python: "3.8"
 
   # Temporary bandaid for https://github.com/PyFilesystem/pyfilesystem2/issues/342
   allow_failures:
     - python: pypy
-    - python: pypy3.5-8.0
+    - python: pypy3.5-7.0
 
 before_install:
   - pip install -U tox tox-travis

setup.py

@@ -22,7 +22,7 @@
     "Topic :: System :: Filesystems",
 ]
 
-REQUIREMENTS = ["appdirs~=1.4.3", "pytz", "setuptools", "six~=1.10", "typing; python_version < '3.5'"]
+REQUIREMENTS = ["appdirs~=1.4.3", "pytz", "setuptools", "six~=1.10"]
 
 setup(
     author="Will McGugan",
@@ -33,6 +33,7 @@
     extras_require={
         "scandir :python_version < '3.5'": ["scandir~=1.5"],
         ":python_version < '3.4'": ["enum34~=1.1.6"],
+        ":python_version < '3.7'": ["typing>=3.5.3"],
         ":python_version < '3.0'": ["backports.os~=0.1"],
     },
     license="MIT",