Drop tests with Python 3.6

GitHub Actions no longer supports Ubuntu 20.04 with
Python 3.6, so test (and support) only 3.7 or later.

Author: benmwebb

.github/workflows/build.yml

@@ -11,8 +11,6 @@ jobs:
         os: [ubuntu-24.04]
         python-version: ['3.8', '3.9', '3.10', '3.11', '3.12', '3.13']
         include:
-        - os: ubuntu-20.04
-          python-version: '3.6'
         - os: ubuntu-22.04
           python-version: '3.7'
     runs-on: ${{ matrix.os }}

python/saliweb/backend/__init__.py

@@ -23,8 +23,8 @@
 
 
 # Version check
-if sys.version_info[0:2] < (3, 6):
-    raise ImportError("This module requires Python 3.6 or later")
+if sys.version_info[0:2] < (3, 7):
+    raise ImportError("This module requires Python 3.7 or later")
 
 
 class InvalidStateError(Exception):