Debug travis unsupported or invalid wheel issue

.travis.yml

@@ -5,7 +5,7 @@ before_install:
   - sudo apt-get update
 # command to install dependencies, e.g. pip install -r requirements.txt --use-mirrors
 install:
-  - pip install arxiv2bib
+  - pip install arxiv2bib || cat ~/.pip/pip.log
   - pip install requesocks
   - pip install pyPDF2
   - pip install tear-pages