build(snapcraft): Fix arm build by using py2 (#671)

snap/snapcraft.yaml

@@ -19,10 +19,14 @@ parts:
       - on arm64:
         - build-essential
         - automake
+        - python-gi
+        - python-gi-dev
       - on armhf:
         - libatomic1
         - build-essential
         - automake
+        - python-gi
+        - python-gi-dev
     source: .
     override-pull: |
       snapcraftctl pull
@@ -55,10 +59,6 @@ parts:
       - PATH: "$SNAPCRAFT_PART_BUILD/node_modules/.bin:$SNAPCRAFT_PART_BUILD/../npm/bin:$PATH"
     override-build: |
       set -e
-      # On arm builds "python" cannot be found. Set python to python3
-      if [ "$ARCH" != "x86_64" ]; then
-        npm config set python "$(which python3)"
-      fi
       # Set COMMIT_TAG before the build begins
       export COMMIT_TAG=$(cat $SNAPCRAFT_PART_BUILD/commit.txt)
       snapcraftctl build