utils/types: add regex types

Add types for regex and bytes_regex. In Python 3, regular expression
objects differ based on whether they were created with a str  or a
bytes instance as the pattern, and can only match against instances of
the corresponding type.

To make sure we always end up using the right version (e.g. pexpect
needs bytes regexes), create functions to do the appropriate
conversions.

devlib/utils/types.py

@@ -26,6 +26,7 @@ is not the best language to use for configuration.
 
 """
 import math
+import sys
 from functools import total_ordering
 
 from past.builtins import basestring
@@ -124,3 +125,38 @@ def bitmask(value):
     if not isinstance(value, int):
         raise ValueError(value)
     return value
+
+
+regex_type = type(re.compile(''))
+
+
+if sys.version_info[0] == 3:
+    def regex(value):
+        if isinstance(value, regex_type):
+            if isinstance(value.pattern, str):
+                return value
+            return re.compile(value.pattern.decode())
+        else:
+            if isinstance(value, bytes):
+                value = value.decode()
+            return re.compile(value)
+
+
+    def bytes_regex(value):
+        if isinstance(value, regex_type):
+            if isinstance(value.pattern, bytes):
+                return value
+            return re.compile(value.pattern.encode(sys.stdout.encoding))
+        else:
+            if isinstance(value, str):
+                value = value.encode(sys.stdout.encoding)
+            return re.compile(value)
+else:
+    def regex(value):
+        if isinstance(value, regex_type):
+            return value
+        else:
+            return re.compile(value)
+
+
+    bytes_regex = regex