Fix snap upload using native deploy provider

This may need generating and setting SNAP_TOKEN as described in
https://docs.travis-ci.com/user/deployment/snaps/

Author: abitrolly

.travis.yml

@@ -1,4 +1,9 @@
 language: python
+dist: xenial
+addons:
+  apt:
+    packages:
+    - snapcraft
 services:
 - docker
 python:
@@ -21,24 +26,20 @@ branches:
   only:
   - master
   - develop
-sudo: required
 jobs:
   include:
   - stage: Pack snap
     env: EMPTY
     before_install: skip
     install: skip
-    script: >
-      docker run -v $(pwd):$(pwd) -w $(pwd) snapcore/snapcraft:stable sh -c "apt-get
-      update && snapcraft"
+    script: snapcraft
     after_success:
     - openssl aes-256-cbc -K $encrypted_8b01c2e263fa_key -iv $encrypted_8b01c2e263fa_iv
       -in .snapcraft/travis_snapcraft.cfg -out .snapcraft/snapcraft.cfg -d
     deploy:
       on:
         branch: master
-      provider: script
-      script: >
-        docker run -v $(pwd):$(pwd) -w $(pwd) snapcore/snapcraft:stable sh -c "apt-get
-        update && snapcraft && snapcraft push *.snap --release edge"
+      provider: snap
+      snap: *.snap
+      channel: edge
       skip_cleanup: true