Unbreak code style checks on Travis CI

Makefile

@@ -1,7 +1,7 @@
 # Makefile for executor.
 #
 # Author: Peter Odding <peter@peterodding.com>
-# Last Change: July 9, 2016
+# Last Change: August 10, 2016
 # URL: https://github.com/xolox/python-executor
 
 WORKON_HOME ?= $(HOME)/.virtualenvs
@@ -41,9 +41,7 @@ reset:
 	$(MAKE) install
 
 check: install
-	@echo "Updating flake8 .." >&2
-	@pip-accel install --upgrade --quiet --requirement=requirements-checks.txt
-	@flake8
+	@scripts/check-code-style.sh
 
 test: install
 	@pip-accel install --quiet coverage pytest pytest-cov

executor/ssh/server.py

@@ -1,7 +1,7 @@
 # Programmer friendly subprocess wrapper.
 #
 # Author: Peter Odding <peter@peterodding.com>
-# Last Change: May 29, 2016
+# Last Change: August 10, 2016
 # URL: https://executor.readthedocs.org
 
 """
@@ -202,7 +202,7 @@ def sshd_path(self):
     @property
     def client_options(self):
         """
-        OpenSSH client options required to connect with the server.
+        Options for the OpenSSH client, required to connect with the server.
 
         This is a dictionary of keyword arguments for :class:`.RemoteCommand`
         to make it connect with the OpenSSH server (assuming the remote command

scripts/check-code-style.sh

@@ -0,0 +1,16 @@
+#!/bin/bash -e
+
+# I value automated code style checks that break my Travis CI builds but I also
+# value compatibility with Python 2.6, however recently it seems that flake8
+# has dropped Python 2.6 compatibility [1]. That's only fair, but now I need to
+# work around it, hence this trivial script :-).
+#
+# [1] https://travis-ci.org/xolox/python-executor/jobs/151190070
+
+if python -c 'import sys; sys.exit(0 if sys.version_info[:2] >= (2, 7) else 1)'; then
+  echo "Updating installation of flake8 .." >&2
+  pip-accel install --upgrade --quiet --requirement=requirements-checks.txt
+  flake8
+else
+  echo "Skipping code style checks on Python 2.6 .." >&2
+fi