added upper version constraint for pycairo keep compatibility with python3.5

Pipfile

@@ -6,6 +6,11 @@ name = "pypi"
 [packages]
 systemctl-mqtt = {editable = true,path = "."}
 
+# python3.5 compatibility
+# systemctl-mqtt > PyGObject > pycairo
+# https://github.com/pygobject/pycairo/commit/6fb84db03704e98acedda3514680a62e05d1b80f#diff-60f61ab7a8d1910d86d9fda2261620314edcae5894d5aaa236b821c7256badd7R613
+pycairo = "<1.20"
+
 [dev-packages]
 # black requires python>=3.6
 # https://github.com/psf/black/commit/e74117f172e29e8a980e2c9de929ad50d3769150#diff-2eeaed663bd0d25b7e608891384b7298R51

Pipfile.lock

@@ -1,7 +1,7 @@
 {
     "_meta": {
         "hash": {
-            "sha256": "6f1f8ab8743aa4a5323271a7b95dade3884dac8cfaf1271368c63919fca2bea3"
+            "sha256": "a47b111547594778f938ff29d318db9c387a8ef67e83007ae61383852467905d"
         },
         "pipfile-spec": 6,
         "requires": {
@@ -32,6 +32,7 @@
             "hashes": [
                 "sha256:2c143183280feb67f5beb4e543fd49990c28e7df427301ede04fc550d3562e84"
             ],
+            "index": "pypi",
             "version": "==1.19.1"
         },
         "pygobject": {