py3: Stop running on Python 2 in Travis.

This clears the way to dropping logic in lots of places
for supporting Python 2.

.travis.yml

@@ -43,9 +43,8 @@ env:
   global:
     - BOTO_CONFIG=/tmp/nowhere
 language: python
-# We run all of our test suites for both Python 2.7 and 3.4, with the
-# exception of static analysis, which is just run once (and checks
-# against both Python versions).
+# Our test suites generally run on Python 3.4, the version in
+# Ubuntu 14.04 trusty, which is the oldest OS release we support.
 matrix:
   include:
     # Travis will actually run the jobs in the order they're listed here;
@@ -60,12 +59,6 @@ matrix:
       env: TEST_SUITE=backend
     - python: "3.4"
       env: TEST_SUITE=production
-    - python: "2.7"
-      env: TEST_SUITE=frontend
-    - python: "2.7"
-      env: TEST_SUITE=backend
-    - python: "2.7"
-      env: TEST_SUITE=production
 sudo: required
 services:
 - docker

tools/provision

@@ -19,19 +19,10 @@ LOG_PATH="../var/log/provision.log"
 
 echo "PROVISIONING STARTING." >> $LOG_PATH
 
-PROVISION_PATH="./lib/provision.py"
-if [ -n "$TRAVIS" ]; then
-    # In CI, we let PATH provide the Python version.
-    PROVISION_CMD=("$PROVISION_PATH")
-else
-    # In dev, we force Python 3.
-    PROVISION_CMD=(python3 "$PROVISION_PATH")
-fi
-
 # PYTHONUNBUFFERED is important to ensure that tracebacks don't get
 # lost far above where they should be in the output.
 export PYTHONUNBUFFERED=1
-"${PROVISION_CMD[@]}" "$@" 2>&1 | tee -a "$LOG_PATH"
+python3 ./lib/provision.py "$@" 2>&1 | tee -a "$LOG_PATH"
 failed=${PIPESTATUS[0]}
 
 if [ $failed = 1 ]; then

tools/travis/activate-venv

@@ -1,11 +1,4 @@
 #!/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
-
+source /srv/zulip-py3-venv/bin/activate
 echo "Using $VIRTUAL_ENV"