ModuleNotFoundError: No module named 'spacy.symbols'

[kkorovesis]

How to reproduce the problem

No lemmatization working using latest spacy version and 'el_core_news_md'. So I turn to this repository where:

pip install -r requirements.txt
python3 -m spacy download el_core_web_sm

Traceback (most recent call last):
  File "/home/konstantinos/.pyenv/versions/3.6.8/lib/python3.6/runpy.py", line 183, in _run_module_as_main
    mod_name, mod_spec, code = _get_module_details(mod_name, _Error)
  File "/home/konstantinos/.pyenv/versions/3.6.8/lib/python3.6/runpy.py", line 142, in _get_module_details
    return _get_module_details(pkg_main_name, error)
  File "/home/konstantinos/.pyenv/versions/3.6.8/lib/python3.6/runpy.py", line 109, in _get_module_details
    __import__(pkg_name)
  File "/home/konstantinos/Repositories/gsoc2018-spacy/spacy/__init__.py", line 4, in <module>
    from .cli.info import info as cli_info
  File "/home/konstantinos/Repositories/gsoc2018-spacy/spacy/cli/__init__.py", line 1, in <module>
    from .download import download
  File "/home/konstantinos/Repositories/gsoc2018-spacy/spacy/cli/download.py", line 11, in <module>
    from .link import link
  File "/home/konstantinos/Repositories/gsoc2018-spacy/spacy/cli/link.py", line 9, in <module>
    from ..util import prints
  File "/home/konstantinos/Repositories/gsoc2018-spacy/spacy/util.py", line 20, in <module>
    from .symbols import ORTH
ModuleNotFoundError: No module named 'spacy.symbols'

Your Environment

Operating System:
NAME="Ubuntu"
VERSION="18.04.3 LTS (Bionic Beaver)"
ID=ubuntu
ID_LIKE=debian
PRETTY_NAME="Ubuntu 18.04.3 LTS"
VERSION_ID="18.04"
HOME_URL="https://www.ubuntu.com/"
SUPPORT_URL="https://help.ubuntu.com/"
BUG_REPORT_URL="https://bugs.launchpad.net/ubuntu/"
PRIVACY_POLICY_URL="https://www.ubuntu.com/legal/terms-and-policies/privacy-policy"
VERSION_CODENAME=bionic
UBUNTU_CODENAME=bionic

Python Version Used:
Python 3.6.8

spaCy Version Used:
spacy==2.0.12.dev0
spacy-langdetect==0.1.2

Environment Information: