Add linter: Make sure we explicitly open all text files using UTF-8 or ASCII encoding in Python

test/lint/lint-python-utf8-encoding.sh

@@ -0,0 +1,19 @@
+#!/bin/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.
+#
+# Make sure we explicitly open all text files using UTF-8 (or ASCII) encoding to
+# avoid potential issues on the BSDs where the locale is not always set.
+
+EXIT_CODE=0
+OUTPUT=$(git grep " open(" -- "*.py" | grep -vE "encoding=.(ascii|utf8|utf-8)." | grep -vE "open\([^,]*, ['\"][^'\"]*b[^'\"]*['\"]")
+if [[ ${OUTPUT} != "" ]]; then
+    echo "Python's open(...) seems to be used to open text files without explicitly"
+    echo "specifying encoding=\"utf8\":"
+    echo
+    echo "${OUTPUT}"
+    EXIT_CODE=1
+fi
+exit ${EXIT_CODE}