Travis: no fail on pep8

pep8.travis.sh

@@ -0,0 +1,12 @@
+#!/bin/sh
+pep8 \
+  setup.py \
+  acme \
+  letsencrypt \
+  letsencrypt-apache \
+  letsencrypt-nginx \
+  letsencrypt-compatibility-test \
+  letshelp-letsencrypt \
+  || echo "PEP8 checking failed, but it's ignored in Travis"
+
+# echo exits with 0

tox.ini

@@ -37,7 +37,7 @@ basepython = python2.7
 # continue, but tox return code will reflect previous error
 commands =
     pip install -r requirements.txt -e acme -e .[dev] -e letsencrypt-apache -e letsencrypt-nginx -e letsencrypt-compatibility-test -e letshelp-letsencrypt
-    pep8 setup.py acme letsencrypt letsencrypt-apache letsencrypt-nginx letsencrypt-compatibility-test letshelp-letsencrypt
+    ./pep8.travis.sh
     pylint --rcfile=.pylintrc letsencrypt
     pylint --rcfile=.pylintrc acme/acme
     pylint --rcfile=.pylintrc letsencrypt-apache/letsencrypt_apache