ci: install dependencies

* Install GTK dev dependencies
* Add requirements.txt
* Fix error that happens on CI only (?)

Author: MightyCreak

.github/workflows/main.yml

@@ -23,7 +23,7 @@ jobs:
     - name: Pylint
       uses: cclauss/GitHub-Action-for-pylint@master
       with:
-        args: "pylint src/**/*.py"
+        args: "apk add --no-cache gtk+3.0-dev gobject-introspection-dev ; pip install -r requirements.txt ; pylint src/**/*.py"
 
   meson-build-test:
     runs-on: ubuntu-latest

requirements.txt

@@ -0,0 +1,2 @@
+PyGObject~=3.40
+pylint~=2.11

src/diffuse/dialogs.py

@@ -110,6 +110,7 @@ def get_encoding(self):
     def get_revision(self):
         return self.revision.get_text()
 
+    # pylint: disable-next=arguments-differ
     def get_filename(self):
         # convert from UTF-8 string to unicode
         return Gtk.FileChooserDialog.get_filename(self) # pylint: disable=no-member