travis: add -y to all apt-get

.travis.yml

@@ -15,14 +15,14 @@ virtualenv:
 
 before_install:
   - sudo apt-get update -qq
-  - sudo apt-get install texlive-latex-base texlive-latex-extra
-  - sudo apt-get install python-scipy python3-scipy  # for ImageHash
-  - sudo apt-get install poppler-utils
-  - sudo apt-get install pandoc
-  - sudo apt-get build-dep python-matplotlib python3-matplotlib
+  - sudo apt-get -y install texlive-latex-base texlive-latex-extra
+  - sudo apt-get -y install python-scipy python3-scipy  # for ImageHash
+  - sudo apt-get -y install poppler-utils
+  - sudo apt-get -y install pandoc
+  - sudo apt-get -y build-dep python-matplotlib python3-matplotlib
   # Dependencies of Pillow, see
   # <https://pillow.readthedocs.org/en/latest/installation.html#linux-installation>.
-  - sudo apt-get install libtiff5-dev libjpeg8-dev zlib1g-dev libfreetype6-dev liblcms2-dev libwebp-dev tcl8.6-dev tk8.6-dev python-tk
+  - sudo apt-get -y install libtiff5-dev libjpeg8-dev zlib1g-dev libfreetype6-dev liblcms2-dev libwebp-dev tcl8.6-dev tk8.6-dev python-tk
 
 install:
   - pip install -r requirements.txt