use Django 2.0.x, not 2.1.x

2.1.x requires >=Python3.5, and current openbabel python RPM uses
Python 3.4

.gitlab-ci.yml

@@ -24,31 +24,6 @@ test-centos7-p34:
   - pip3 -V
   - pip3 install -r requirements-centos.txt
   - python3 manage.py test
-test-centos7-p35:
-  image: centos:centos7
-  stage: test
-  script:
-  - yum install -y epel-release
-  - yum install -y wget
-  - wget https://centos7.iuscommunity.org/ius-release.rpm
-  - rpm -Uvh ius-release*.rpm
-  - yum install -y python35u python35u-libs python35u-devel python35u-pip
-  - yum install -y gcc graphviz graphviz-devel
-  - yum install -y httpd httpd-devel
-  - yum install -y gcc-c++
-  - yum update -y
-  #- yum install -y desktop-file-utils inchi-devel libxml2-devel swig wxGTK-devel ImageMagick perl-devel perl-generators
-  - yum install -y swig # openbabel pip dep
-  - yum install -y wxBase wxGTK inchi  #openbabel rpm deps
-  - wget https://gitlab.pasteur.fr/hub/openbabel4ippidb/raw/master/rpmbuild/RPMS/x86_64/openbabel-libs-2.4.1-15.PR1829.py3.el7.x86_64.rpm
-  - wget https://gitlab.pasteur.fr/hub/openbabel4ippidb/raw/master/rpmbuild/RPMS/x86_64/openbabel-devel-2.4.1-15.PR1829.py3.el7.x86_64.rpm
-  - wget https://gitlab.pasteur.fr/hub/openbabel4ippidb/raw/master/rpmbuild/RPMS/x86_64/openbabel-2.4.1-15.PR1829.py3.el7.x86_64.rpm
-  - wget https://gitlab.pasteur.fr/hub/openbabel4ippidb/raw/master/rpmbuild/RPMS/x86_64/python3-openbabel-2.4.1-15.PR1829.py3.el7.x86_64.rpm
-  - rpm -Uvh *.rpm
-  - cd ippisite
-  - pip3 -V
-  - pip3 install -r requirements-centos.txt
-  - python3 manage.py test
 deploy-webserver:
   stage: deploy
   before_script:

ippisite/requirements-core.txt

 # django and extensions
-Django>=2.1.5
+Django>=2.0,<2.1
 django-extensions
 django-formtools
 django-debug-toolbar