ci: run all CI on Python 3

i.e. drop support for Python 2

.gitlab-ci.yml

@@ -8,31 +8,31 @@ include:
     file: python.yml
 
 .syntax:
+  # https://computing.docs.ligo.org/gitlab-ci-templates/python/#.python:coverage
+  extends: .python:coverage
   stage: Syntax check
   needs: []
-  variables:
-    PYTHON: "python3"
   script:
     # test that we can execute the WSGI app:
-    - ${PYTHON} "${CI_PROJECT_DIR}/src/application.py"
+    - python3 -m coverage run --source src "${CI_PROJECT_DIR}/src/application.py"
 
 syntax:el7:
   extends: .syntax
   image: igwn/base:el7
-  variables:
-    PYTHON: "python2"
   before_script:
     - yum -y --setopt=obsoletes=0 install
         m2crypto
-        python2
-        python2-glue
-        pyodbc
+        python3
+        python3-coverage
+        python3-lscsoft-glue
+        python3-m2crypto
+        python3-pip
+    # pyodbc not packaged for python3 on EL7, so build it from scratch
+    - yum -y install gcc
+    - python3 -m pip install pyodbc
 
 syntax:rl8:
-  extends:
-    # https://computing.docs.ligo.org/gitlab-ci-templates/python/#.python:coverage
-    - .python:coverage
-    - .syntax
+  extends: .syntax
   image: igwn/base:el8-testing
   before_script:
     - yum -y install
@@ -41,5 +41,3 @@ syntax:rl8:
         python3-lscsoft-glue
         python3-m2crypto
         python3-pyodbc
-  script:
-    - ${PYTHON} -m coverage run --source src "${CI_PROJECT_DIR}/src/application.py"