build: python 3 compatibility

src/Makefile.qt.include

@@ -403,7 +403,7 @@ SECONDARY: $(QT_QM)
 
 $(srcdir)/qt/bitcoinstrings.cpp: $(libbitcoin_server_a_SOURCES) $(libbitcoin_wallet_a_SOURCES)
 	@test -n $(XGETTEXT) || echo "xgettext is required for updating translations"
-	$(AM_V_GEN) cd $(srcdir); XGETTEXT=$(XGETTEXT) ../share/qt/extract_strings_qt.py $^
+	$(AM_V_GEN) cd $(srcdir); XGETTEXT=$(XGETTEXT) $(PYTHON) ../share/qt/extract_strings_qt.py $^
 
 translate: $(srcdir)/qt/bitcoinstrings.cpp $(QT_FORMS_UI) $(QT_FORMS_UI) $(BITCOIN_QT_CPP) $(BITCOIN_QT_H) $(BITCOIN_MM)
 	@test -n $(LUPDATE) || echo "lupdate is required for updating translations"

src/Makefile.test.include

@@ -133,10 +133,10 @@ bitcoin_test_clean : FORCE
 
 check-local:
 	@echo "Running test/bitcoin-util-test.py..."
-	$(AM_V_at)srcdir=$(srcdir) PYTHONPATH=$(builddir)/test $(srcdir)/test/bitcoin-util-test.py
+	$(AM_V_at)srcdir=$(srcdir) PYTHONPATH=$(builddir)/test $(PYTHON) $(srcdir)/test/bitcoin-util-test.py
 if ENABLE_WALLET
 	@echo "Running test/wallet-utility.py..."
-	$(AM_V_at)srcdir=$(srcdir) PYTHONPATH=$(builddir)/test $(srcdir)/test/wallet-utility.py
+	$(AM_V_at)srcdir=$(srcdir) PYTHONPATH=$(builddir)/test $(PYTHON) $(srcdir)/test/wallet-utility.py
 endif
 	$(AM_V_at)$(MAKE) $(AM_MAKEFLAGS) -C secp256k1 check
 if EMBEDDED_UNIVALUE

src/test/bctest.py

@@ -1,7 +1,7 @@
 # Copyright 2014 BitPay, Inc.
 # Distributed under the MIT software license, see the accompanying
 # file COPYING or http://www.opensource.org/licenses/mit-license.php.
-
+from __future__ import division,print_function,unicode_literals
 import subprocess
 import os
 import json

src/test/bitcoin-util-test.py

@@ -2,7 +2,7 @@
 # Copyright 2014 BitPay, Inc.
 # Distributed under the MIT software license, see the accompanying
 # file COPYING or http://www.opensource.org/licenses/mit-license.php.
-
+from __future__ import division,print_function,unicode_literals
 import os
 import bctest
 import buildenv