Add flake8 to testing

.travis.yml

@@ -13,9 +13,15 @@ matrix:
 install:
     # via https://github.com/angr/angr/issues/52
     - pip install -I --no-use-wheel capstone
-    - pip install --upgrade pep8 pytest-cov pytest
+    - pip install --upgrade pep8 pytest-cov pytest flake8
     - pip install -e .
 
+before_script:
+    # stop the build if there are Python syntax errors or undefined names
+    - flake8 . --count --select=E901,E999,F821,F822,F823 --show-source --statistics
+    # exit-zero treats all errors as warnings.  The GitHub editor is 127 chars wide
+    - flake8 . --count --exit-zero --max-complexity=10 --max-line-length=127 --statistics
+
 script:
     - find . -name \*.py -exec pep8 --ignore=E501 {} \;
-    - py.test ./tests/ -v --cov=idb
+    - py.test ./tests/ -v --cov=idb