Force to use image with Conan 1 because all required packages for building...

Force to use image with Conan 1 because all required packages for building Python are not yet for Conan 2

.gitlab-ci.yml

 variables:
   PYTHON_VERSION: "3.6.13"
+  CONAN_DOCKER_VERSION: "1.59.0"
 
 stages:
   - build
@@ -44,14 +45,14 @@ workflow:
 
 linux-x86_64:
   extends: [".build"]
-  image: gitlab-registry.synchrotron-soleil.fr/software-control-system/containers/conan-docker-tools/conan-el6-gcc91:1.59.0
+  image: gitlab-registry.synchrotron-soleil.fr/software-control-system/containers/conan-docker-tools/conan-el6-gcc91:${CONAN_DOCKER_VERSION}
   variables:
     NAME: "python-${PYTHON_VERSION}-linux-x86_64"
     PYTHON_ROOT: "${CI_PROJECT_DIR}/${NAME}"
 
 test-x86_64:
   extends: [".test"]
-  image: gitlab-registry.synchrotron-soleil.fr/software-control-system/containers/conan-docker-tools/conan-el6-gcc91:1.59.0
+  image: gitlab-registry.synchrotron-soleil.fr/software-control-system/containers/conan-docker-tools/conan-el6-gcc91:${CONAN_DOCKER_VERSION}
   variables:
     NAME: "python-${PYTHON_VERSION}-linux-x86_64"
   needs:
@@ -59,7 +60,7 @@ test-x86_64:
 
 package-x86_64:
   extends: [".package"]
-  image: gitlab-registry.synchrotron-soleil.fr/software-control-system/containers/conan-docker-tools/conan-el6-gcc91
+  image: gitlab-registry.synchrotron-soleil.fr/software-control-system/containers/conan-docker-tools/conan-el6-gcc91:${CONAN_DOCKER_VERSION}
   variables:
     NAME: "python-${PYTHON_VERSION}-linux-x86_64"
   needs:
@@ -68,14 +69,14 @@ package-x86_64:
 
 linux-i686:
   extends: [".build"]
-  image: gitlab-registry.synchrotron-soleil.fr/software-control-system/containers/conan-docker-tools/conan-el6-gcc91-x86
+  image: gitlab-registry.synchrotron-soleil.fr/software-control-system/containers/conan-docker-tools/conan-el6-gcc91-x86:${CONAN_DOCKER_VERSION}
   variables:
     NAME: "python-${PYTHON_VERSION}-linux-i686"
     PYTHON_ROOT: "${CI_PROJECT_DIR}/${NAME}"
 
 test-i686:
   extends: [".test"]
-  image: gitlab-registry.synchrotron-soleil.fr/software-control-system/containers/conan-docker-tools/conan-el6-gcc91-x86
+  image: gitlab-registry.synchrotron-soleil.fr/software-control-system/containers/conan-docker-tools/conan-el6-gcc91-x86:${CONAN_DOCKER_VERSION}
   variables:
     NAME: "python-${PYTHON_VERSION}-linux-i686"
   needs:
@@ -83,7 +84,7 @@ test-i686:
 
 package-i686:
   extends: [".package"]
-  image: gitlab-registry.synchrotron-soleil.fr/software-control-system/containers/conan-docker-tools/conan-el6-gcc91-x86
+  image: gitlab-registry.synchrotron-soleil.fr/software-control-system/containers/conan-docker-tools/conan-el6-gcc91-x86:${CONAN_DOCKER_VERSION}
   variables:
     NAME: "python-${PYTHON_VERSION}-linux-i686"
   needs: