Coerce compiled regex patterns to bytes type in bytes mode

pexpect/spawnbase.py

@@ -138,6 +138,13 @@ def _coerce_expect_string(self, s):
             return s.encode('ascii')
         return s
 
+    # In bytes mode, regex patterns should also be of bytes type
+    def _coerce_expect_re(self, r):
+        p = r.pattern
+        if self.encoding is None and not isinstance(p, bytes):
+            return re.compile(p.encode('utf-8'))
+        return r
+
     def _coerce_send_string(self, s):
         if self.encoding is None and not isinstance(s, bytes):
             return s.encode('utf-8')
@@ -232,6 +239,7 @@ def compile_pattern_list(self, patterns):
             elif p is TIMEOUT:
                 compiled_pattern_list.append(TIMEOUT)
             elif isinstance(p, type(re.compile(''))):
+                p = self._coerce_expect_re(p)
                 compiled_pattern_list.append(p)
             else:
                 self._pattern_type_err(p)