Travis: use xenial for Python 3.7

.travis.yml

@@ -1,46 +1,70 @@
-dist: trusty
-language: python
 cache:
   pip: true
   directories:
   - $HOME/Library/Caches/Homebrew
 
-addons:
-  apt:
-    update: true
-    sources:
-    - sourceline: 'ppa:alex-p/tesseract-ocr'
-    - sourceline: 'ppa:heyarje/libav-11'
-    - sourceline: 'ppa:vshn/ghostscript'
-    packages:
-    - ghostscript
-    - libavcodec56
-    - libavformat56
-    - libavutil54
-    - libexempi3
-    - libffi-dev
-    - pngquant
-    - poppler-utils
-    - qpdf
-    - tesseract-ocr
-    - tesseract-ocr-deu
-    - tesseract-ocr-eng
-    - tesseract-ocr-fra
-
 matrix:
   include:
     - os: linux
+      dist: trusty
       sudo: required
       language: python
       python: "3.5"
+        env:
+        - DIST=trusty
+      addons: *trusty_apt
     - os: linux
+      dist: trusty
       sudo: required
       language: python
       python: "3.6"
+      env:
+        - DIST=trusty
+      addons: &trusty_apt
+        apt:
+          update: true
+          sources:
+          - sourceline: 'ppa:alex-p/tesseract-ocr'
+          - sourceline: 'ppa:heyarje/libav-11'
+          - sourceline: 'ppa:vshn/ghostscript'
+          packages:
+          - ghostscript
+          - libavcodec56
+          - libavformat56
+          - libavutil54
+          - libexempi3
+          - libffi-dev
+          - pngquant
+          - poppler-utils
+          - qpdf
+          - tesseract-ocr
+          - tesseract-ocr-deu
+          - tesseract-ocr-eng
+          - tesseract-ocr-fra
     - os: linux
+      dist: xenial
       sudo: required
       language: python
-      python: "3.7-dev"
+      python: "3.7"
+      env:
+        - DIST=xenial
+      addons:
+        apt:
+          update: true
+          sources:
+          - sourceline: 'ppa:alex-p/tesseract-ocr'
+          packages:
+          - ghostscript
+          - libexempi3
+          - libffi-dev
+          - pngquant
+          - poppler-utils
+          - qpdf
+          - tesseract-ocr
+          - tesseract-ocr-deu
+          - tesseract-ocr-eng
+          - tesseract-ocr-fra
+          - unpaper
     - os: osx
       osx_image: xcode8
       language: generic
@@ -53,9 +77,11 @@ before_install: |
   if [[ "$TRAVIS_OS_NAME" == "linux" ]]; then
     pip3 install --upgrade pip
     pip3 install --upgrade wheel
-    mkdir -p packages
-    wget -q 'https://www.dropbox.com/s/vaq0kbwi6e6au80/unpaper_6.1-1.deb?raw=1' -O packages/unpaper_6.1-1.deb
-    sudo dpkg -i packages/unpaper_6.1-1.deb
+    if [[ "$DIST" == "trusty" ]]; then
+      mkdir -p packages
+      wget -q 'https://www.dropbox.com/s/vaq0kbwi6e6au80/unpaper_6.1-1.deb?raw=1' -O packages/unpaper_6.1-1.deb
+      sudo dpkg -i packages/unpaper_6.1-1.deb
+    fi
   elif [[ "$TRAVIS_OS_NAME" == "osx" ]]; then
     brew update && brew bundle --file=.travis/Brewfile
     pip3 install --upgrade pip