Disable OCR tests on the aged Python 3.5 and Ubuntu Xenial platform

Xenial starts accumulating problems with tesserocr and its tesseract
dependencies (e.g. leptonica development library) and we already
test both OpenCV 3.X and OpenCV 4.X OCR on the newer Bionic and
Focal platforms respectively.

The accumulated restrictions on Python 3.5 are nearly all now.

.travis.yml

@@ -55,6 +55,7 @@ before_script:
 - "/sbin/start-stop-daemon --start --quiet --pidfile /tmp/custom_xvfb_99.pid --make-pidfile
   --background --exec /usr/bin/Xvfb -- :99 -ac -screen 0 1024x768x24"
 - sleep 3  # give xvfb some time to start
+- if [[ $TRAVIS_PYTHON_VERSION == '3.5' ]]; then export DISABLE_OCR=1; fi
 - if [[ $TRAVIS_PYTHON_VERSION == 'pypy3.5' ]]; then export DISABLE_AUTOPY=1; fi
 - if [[ $TRAVIS_PYTHON_VERSION == 'pypy3.5' ]]; then export DISABLE_PYQT=1; fi
 - if [[ $TRAVIS_PYTHON_VERSION == 'pypy3.5' ]]; then export DISABLE_OPENCV=1; fi

packaging/packager_deb.sh

@@ -21,9 +21,13 @@ else
     apt-get -y install python3-opencv
 fi
 # text matching
-apt-get -y install tesseract-ocr libtesseract-dev
-apt-get -y install g++ pkg-config
-pip3 install pytesseract==0.3.4 tesserocr==2.5.1
+if [[ $distro_version == "xenial" ]]; then
+    export DISABLE_OCR=1
+else
+    apt-get -y install tesseract-ocr libtesseract-dev
+    apt-get -y install g++ pkg-config
+    pip3 install pytesseract==0.3.4 tesserocr==2.5.1
+fi
 # deep learning
 pip3 install torch==1.4.0 torchvision==0.5.0
 # screen controlling