change six installation

.gitlab-ci.yml

@@ -42,7 +42,7 @@ tests (from scratch):
     - ./CI/update_badge.sh > /dev/null
   script:
     - pip install --upgrade pip
-    - pip install numpy wheel six
+    - pip install numpy wheel six==1.15.0
     - zypper --non-interactive install binutils libproj-devel gdal-devel
     - zypper --non-interactive install proj geos-devel
     #    - cat requirements.txt | cut -f1 -d"#" | sed '/^\s*$/d' | xargs -L 1 pip install

requirements.txt

@@ -51,7 +51,7 @@ PyYAML==5.4.1
 requests==2.25.1
 scipy==1.5.4
 seaborn==0.11.1
---ignore-installed six==1.15.0
+six==1.15.0
 statsmodels==0.12.2
 tabulate==0.8.8
 tensorboard==1.13.1