Deprecate support for Python 3.5

Python 3.5 has been EOL for more than a year now, and it's causing failures
in the CI testing. So let's just drop the support. Python 3.6 is also
end-of-life, but for now supporting it does not seem to have any concrete
costs, so let's keep it around until that changes.

Signed-off-by: Toke Høiland-Jørgensen <toke@toke.dk>

.github/workflows/selftests.yml

@@ -11,16 +11,10 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python: ["3.5", "3.6", "3.7", "3.8", "3.9", "3.10"]
+        python: ["3.6", "3.7", "3.8", "3.9", "3.10"]
         matplotlib: ["2.1", "2.2", "3.0", "3.1", "3.2", "3.3", "3.4", "3.5"]
         pyqt: ["PyQt5", "PySide2"]
         include:
-          - python: "3.5"
-            matplotlib: "1.5"
-            pyqt: PyQt5
-          - python: "3.5"
-            matplotlib: "2.0"
-            pyqt: PyQt5
           - python: "3.6"
             matplotlib: "1.5"
             pyqt: PyQt5
@@ -34,16 +28,6 @@ jobs:
             matplotlib: "2.0"
             pyqt: PyQt5
         exclude:
-          - python: "3.5"
-            matplotlib: "3.1"
-          - python: "3.5"
-            matplotlib: "3.2"
-          - python: "3.5"
-            matplotlib: "3.3"
-          - python: "3.5"
-            matplotlib: "3.4"
-          - python: "3.5"
-            matplotlib: "3.5"
           - python: "3.6"
             matplotlib: "3.4"
           - python: "3.6"

flent/__init__.py

@@ -33,8 +33,8 @@ def handle_sigterm(sig, frame):
 
 
 def run_flent(gui=False):
-    if sys.version_info[:2] < (3, 5):
-        sys.stderr.write("Sorry, Flent requires v3.5 or later of Python.\n")
+    if sys.version_info[:2] < (3, 6):
+        sys.stderr.write("Sorry, Flent requires v3.6 or later of Python.\n")
         sys.exit(1)
     try:
         try: