Begin incorporating Python unit tests into build

We now build a separate APE binary for each test so they can run in
parallel. We've got 148 tests running fast and stable so far.

third_party/python/Lib/email/base64mime.py

@@ -36,6 +36,7 @@ __all__ = [
 
 from base64 import b64encode
 from binascii import b2a_base64, a2b_base64
+from encodings import raw_unicode_escape
 
 CRLF = '\r\n'
 NL = '\n'

third_party/python/Lib/email/charset.py

@@ -17,6 +17,29 @@ import email.quoprimime
 from email import errors
 from email.encoders import encode_7or8bit
 
+from encodings import (
+    base64_codec,
+    quopri_codec,
+    iso8859_1,
+    iso8859_2,
+    iso8859_3,
+    iso8859_4,
+    iso8859_9,
+    iso8859_10,
+    iso8859_13,
+    iso8859_14,
+    iso8859_15,
+    iso8859_16,
+    iso8859_10,
+    cp1252,
+    big5,
+    gb2312,
+    euc_jp,
+    shift_jis,
+    iso2022_jp,
+    koi8_r,
+    utf_8,
+)
 
 
 # Flags for types of header encodings

third_party/python/Lib/email/message.py

@@ -11,13 +11,18 @@ import uu
 import quopri
 from io import BytesIO, StringIO
 
+from encodings import (
+    base64_codec,
+    quopri_codec,
+    raw_unicode_escape,
+)
+
 # Intrapackage imports
 from email import utils
 from email import errors
 from email._policybase import Policy, compat32
 from email import charset as _charset
 from email._encoded_words import decode_b
-from email.iterators import walk
 Charset = _charset.Charset
 
 SEMISPACE = '; '
@@ -940,6 +945,7 @@ class Message:
         return c_d
 
     # I.e. def walk(self): ...
+    from email.iterators import walk
 
 
 class MIMEPart(Message):