Travis: build partly working on trusty; tweak requirements again

The build is #122
https://travis-ci.org/jbarlow83/OCRmyPDF/builds/148255615

Errors seem to be related to either Ghostscript or leptonica? Maybe
-dSAFER?

.travis.yml

@@ -18,6 +18,7 @@ before_cache:
 
 before_install:
     # Ubuntu packages
+    - sudo add-apt-repository ppa:vshn/ghostscript -y  # for ghostscript 9.16 (trusty has 9.10)
     - sudo add-apt-repository ppa:heyarje/libav-11 -y  # for libav11, which is for unpaper
     - sudo apt-get update -qq  # must go after all add-apt-repo
     - sudo apt-get install -y ghostscript tesseract-ocr tesseract-ocr-deu tesseract-ocr-eng tesseract-ocr-fra qpdf poppler-utils libavformat56 libavcodec56 libavutil54 libffi-dev

requirements.txt

@@ -1,6 +1,9 @@
+# requirements.txt can be used to replicate the developer's build environment
+# setup.py lists a separate set of requirements that are looser to simplify
+# installation
 ruffus==2.6.3
-Pillow==3.1.1
+Pillow==3.3.0
 reportlab==3.2.0
-PyPDF2==1.25.1
-img2pdf==0.2
+PyPDF2==1.26
+img2pdf==0.2.1
 cffi==1.5.2

setup.py

@@ -217,12 +217,12 @@ setup(
         'ocrmypdf/lib/compile_leptonica.py:ffi'
     ],
     install_requires=[
-        'ruffus==2.6.3',        # ocrmypdf implements a 2.6.3 workaround
-        'Pillow>=3.0.0',        # just seemed right
-        'reportlab>=3.1.44',    # oldest version with sane image handling
+        'ruffus==2.6.3',        # pinned - ocrmypdf implements a 2.6.3 workaround
+        'Pillow>=3.1.0',        # Pillow is pretty stable
+        'reportlab>=3.2.0',     # oldest released version with sane image handling
         'PyPDF2>=1.26',         # pure Python, so track HEAD closely
         'img2pdf>=0.2.1',       # pure Python, so track HEAD closely
-        'cffi>=1.5.0'           # oldest version with stable API
+        'cffi>=1.5.0'           # oldest version ever tested
     ],
     tests_require=tests_require,
     entry_points={