fix: correctly fallback to pure python when cython is missing (#130)

src/dbus_fast/_private/_cython_compat.py

@@ -1,4 +1,12 @@
+"""Stub for when Cython is not available."""
+
+
 class FakeCython:
+    """Stub for when Cython is not available."""
+
     @property
-    def compiled(self):
+    def compiled(self) -> bool:
         return False
+
+
+FAKE_CYTHON = FakeCython()

src/dbus_fast/_private/unmarshaller.py

@@ -142,7 +142,7 @@ class MarshallerStreamEndError(Exception):
 try:
     import cython
 except ImportError:
-    from ._cython_compat import FakeCython as cython
+    from ._cython_compat import FAKE_CYTHON as cython
 
 #
 # Alignment padding is handled with the following formula below
@@ -527,7 +527,7 @@ class Unmarshaller:
             self._body_len = _cast_uint32_native(self._buf, 4)  # pragma: no cover
             self._serial = _cast_uint32_native(self._buf, 8)  # pragma: no cover
             self._header_len = _cast_uint32_native(self._buf, 12)  # pragma: no cover
-        if endian == LITTLE_ENDIAN:
+        elif endian == LITTLE_ENDIAN:
             (
                 self._body_len,
                 self._serial,