Always pass an encoding to open() using text mode

Otherwise we'll end up using the locale encoding. While it's usually utf-8,
that's not the case on Windows.

There is one place where a file with filenames is passed, not sure there
so I left it and passed a explicit None.

3 files changed, 3 insertions, 3 deletions

diff --git a/tests/scanner/test_maintransformer.py b/tests/scanner/test_maintransformer.py
index abf3ee73..f0e2d629 100644
--- a/tests/scanner/test_maintransformer.py
+++ b/tests/scanner/test_maintransformer.py
@@ -16,7 +16,7 @@ def create_scanner_from_source_string(source):
     tmp_fd, tmp_name = tempfile.mkstemp(suffix='.h', text=True)
 
     try:
-        with os.fdopen(tmp_fd, 'wt') as file:
+        with os.fdopen(tmp_fd, 'w', encoding='utf-8') as file:
             file.write(source)
         ss.parse_files([tmp_name])
     finally:
diff --git a/tests/scanner/test_transformer.py b/tests/scanner/test_transformer.py
index c6fbf4e7..3feed441 100644
--- a/tests/scanner/test_transformer.py
+++ b/tests/scanner/test_transformer.py
@@ -18,7 +18,7 @@ def create_scanner_from_source_string(source):
     tmp_fd, tmp_name = tempfile.mkstemp(suffix='.h', text=True)
 
     try:
-        with os.fdopen(tmp_fd, 'wt') as file:
+        with os.fdopen(tmp_fd, 'w', encoding='utf-8') as file:
             file.write(source)
         ss.parse_files([tmp_name])
     finally:
diff --git a/tests/warn/warningtester.py b/tests/warn/warningtester.py
index fedd3a59..3bb9e4b2 100644
--- a/tests/warn/warningtester.py
+++ b/tests/warn/warningtester.py
@@ -78,7 +78,7 @@ def _diff(a, b):
 
 
 def _extract_expected(filename):
-    fd = open(filename, 'r')
+    fd = open(filename, 'r', encoding='utf-8')
     data = fd.read()
     fd.close()