Run tools/lint-all on Travis in python 3.

.travis.yml

@@ -1,3 +1,4 @@
+dist: trusty
 before_install:
    - nvm install 0.10
 install:
@@ -29,6 +30,9 @@ matrix:
   include:
     - python: "3.4"
       env: TEST_SUITE=mypy
+    - python: "3.4"
+      env: TEST_SUITE=lint-all
+      sudo: required
 # command to run tests
 script:
   - ./tools/travis/$TEST_SUITE

tools/travis/activate-venv

@@ -0,0 +1,11 @@
+#!/bin/bash
+
+py_version="$(python -c 'import sys; print(sys.version_info[0])')"
+
+if [ "$py_version" == 2 ]; then
+    source /srv/zulip-venv/bin/activate
+else
+    source /srv/zulip-py3-venv/bin/activate
+fi
+
+echo "Using $VIRTUAL_ENV"

tools/travis/lint-all

@@ -0,0 +1,31 @@
+#!/bin/bash
+
+source tools/travis/activate-venv
+
+echo "+ ./tools/lint-all"
+./tools/lint-all
+retcode="$?"
+
+echo
+if [ "$retcode" == 0 ]; then
+    echo "tools/lint-all detected no errors on Python 3!"
+else
+    echo "tools/lint-all threw some errors in when run using python 3."
+    echo "This indicates that there is either a bug in your code or your code doesn't"
+    echo "follow our style guidelines (http://zulip.readthedocs.io/en/latest/code-style.html)."
+    echo
+    echo "The most likely problem is that tools/lint-all also fails with Python "
+    echo "2, which you can check locally by simply running `tools/lint-all` in your "
+    echo "Zulip development environment."
+    echo
+    echo "To run tools/lint-all locally in python 3, you must first install"
+    echo 'the required packages.  To do that, run `python3 provision.py` then'
+    echo '`source /srv/zulip-py3-venv` and then `tools/lint-all`.'
+    echo
+    echo "You can also install tools/lint-all's dependencies manually:"
+    echo "It requires six, typing (check their versions from requirements/common.txt)."
+    echo "and pyflakes (check its version from requirements/dev.txt). It is likely that"
+    echo "you already have a python 3 virtualenv installed in /srv/zulip-py3-venv, but"
+    echo "you might still need to install the dependencies listed above."
+    exit 1
+fi

tools/travis/setup-lint-all

@@ -0,0 +1,4 @@
+#!/bin/bash
+set -e
+set -x
+python tools/provision.py --travis