move remaining travis build steps into individual files

.travis.yml

@@ -49,9 +49,9 @@ jobs:
       language: python
       python: '3.6'
       install:
-        - travis_retry pip install flake8
+        - source .travis/lint_04_install.sh
       before_script:
-        - git fetch --unshallow
+        - source .travis/lint_05_before_script.sh
       script:
         - source .travis/lint_06_script.sh
 # ARM

.travis/lint_04_install.sh

@@ -0,0 +1,9 @@
+#!/usr/bin/env bash
+#
+# Copyright (c) 2018 The Bitcoin Core developers
+# Distributed under the MIT software license, see the accompanying
+# file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+export LC_ALL=C
+
+travis_retry pip install flake8

.travis/lint_05_before_script.sh

@@ -0,0 +1,9 @@
+#!/usr/bin/env bash
+#
+# Copyright (c) 2018 The Bitcoin Core developers
+# Distributed under the MIT software license, see the accompanying
+# file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+export LC_ALL=C
+
+git fetch --unshallow

.travis/lint_06_script.sh

@@ -3,8 +3,6 @@
 # Copyright (c) 2018 The Bitcoin Core developers
 # Distributed under the MIT software license, see the accompanying
 # file COPYING or http://www.opensource.org/licenses/mit-license.php.
-#
-# Check for new lines in diff that introduce trailing whitespace.
 
 export LC_ALL=C