Always read python source using UTF-8

CHANGELOG.rst

@@ -2,6 +2,10 @@
 Release History
 ---------------
 
+2.2.1
+- Python source is now always read using utf-8, even if default encoding for
+  reading files is set otherwise.
+
 2.2.0
 
 - Added `--skip-incompatible` flag to `pip-extra-reqs`, which makes it ignore

pip_check_reqs/__init__.py

@@ -1 +1 @@
-__version__ = '2.2.0'
+__version__ = '2.2.1'

pip_check_reqs/common.py

@@ -119,7 +119,7 @@ def find_imported_modules(options):
                 log.info('ignoring: %s', os.path.relpath(filename))
                 continue
             log.debug('scanning: %s', os.path.relpath(filename))
-            with open(filename) as f:
+            with open(filename, encoding='utf-8') as f:
                 content = f.read()
             vis.set_location(filename)
             vis.visit(ast.parse(content))

tests/test_common.py

@@ -106,7 +106,7 @@ class FakeFile():
             'from . import friend',
         ]
 
-        def __init__(self, filename):
+        def __init__(self, filename, encoding=None):
             pass
 
         def read(self):
@@ -196,3 +196,32 @@ def ignore_reqs(self, modname):
         requirements_filename=str(fake_requirements_file),
     )
     assert not reqs
+
+
+def test_find_imported_modules_sets_encoding_to_utf8_when_reading(tmp_path):
+    (tmp_path / 'module.py').touch()
+
+    class options:
+        paths = [tmp_path]
+
+        def ignore_files(*_):
+            return False
+
+    expected_encoding = 'utf-8'
+    used_encoding = None
+
+    original_open = common.__builtins__['open']
+
+    def mocked_open(*args, **kwargs):
+        # As of Python 3.9, the args to open() are as follows:
+        # file, mode, buffering, encoding, erorrs, newline, closedf, opener
+        nonlocal used_encoding
+        if 'encoding' in kwargs:
+            used_encoding = kwargs['encoding']
+        return original_open(*args, **kwargs)
+
+    common.__builtins__['open'] = mocked_open
+    common.find_imported_modules(options)
+    common.__builtins__['open'] = original_open
+
+    assert used_encoding == expected_encoding