Included contrib nametrans_imap_to_utf8.py

Script file to use as nametrans to convert IMAP UTF-7 to UTF-8.

Please, take a look of issue #23

https://github.com/OfflineIMAP/offlineimap3/issues/23

Thanks a lot to @dnebauer and @sudipm-mukherjee

Closes #23

contrib/nametrans_imap_to_utf8.py

@@ -0,0 +1,43 @@
+"""
+convert_utf7_to_utf8 used in nametrans
+
+Main code: Rodolfo García Peñas (kix) @thekix
+Updated regex by @dnebauer
+
+Please, check https://github.com/OfflineIMAP/offlineimap3/issues/23
+for more info.
+"""
+import re
+
+
+def convert_utf7_to_utf8(str_imap):
+    """
+    This function converts an IMAP_UTF-7 string object to UTF-8.
+    It first replaces the ampersand (&) character with plus character (+)
+    in the cases of UTF-7 character and then decode the string to utf-8.
+
+    If the str_imap string is already UTF-8, return it.
+
+    For example, "abc&AK4-D" is translated to "abc+AK4-D"
+    and then, to "abc@D"
+
+    Example code:
+    my_string = "abc&AK4-D"
+    print(convert_utf7_to_utf8(my_string))
+
+    Args:
+        bytes_imap: IMAP UTF7 string
+
+    Returns: UTF-8 string
+
+    Source: https://github.com/OfflineIMAP/offlineimap3/issues/23
+
+    """
+    try:
+        str_utf7 = re.sub(r'&(\w{3}\-)', '+\\1', str_imap)
+        str_utf8 = str_utf7.encode('utf-8').decode('utf_7')
+        return str_utf8
+    except UnicodeDecodeError:
+        # error decoding because already utf-8, so return original string
+        return str_imap
+