fix pip compability

[crmplease]

root@c216ef2f0515:/tmp/sqlalchemy-pagination# pip3 install .
Processing /tmp/sqlalchemy-pagination
    ERROR: Command errored out with exit status 1:
     command: /usr/local/bin/python -c 'import sys, setuptools, tokenize; sys.argv[0] = '"'"'/tmp/pip-req-build-c5lax5jd/setup.py'"'"'; __file__='"'"'/tmp/pip-req-build-c5lax5jd/setup.py'"'"';f=getattr(tokenize, '"'"'open'"'"', open)(__file__);code=f.read().replace('"'"'\r\n'"'"', '"'"'\n'"'"');f.close();exec(compile(code, __file__, '"'"'exec'"'"'))' egg_info --egg-base /tmp/pip-pip-egg-info-oa02jt6n
         cwd: /tmp/pip-req-build-c5lax5jd/
    Complete output (9 lines):
    Traceback (most recent call last):
      File "<string>", line 1, in <module>
      File "/tmp/pip-req-build-c5lax5jd/setup.py", line 39, in <module>
        tests_require=requirements('requirements-dev.txt'),
      File "/tmp/pip-req-build-c5lax5jd/setup.py", line 13, in requirements
        return [str(r.req) for r in reqs]
      File "/tmp/pip-req-build-c5lax5jd/setup.py", line 13, in <listcomp>
        return [str(r.req) for r in reqs]
    AttributeError: 'ParsedRequirement' object has no attribute 'req'
    ----------------------------------------
ERROR: Command errored out with exit status 1: python setup.py egg_info Check the logs for full command output.
WARNING: You are using pip version 20.2.2; however, version 20.2.3 is available.
You should consider upgrading via the '/usr/local/bin/python -m pip install --upgrade pip' command.