Adding cython v0.20.2 in third-party.

third_party/cython/src/Cython/Plex/Errors.py

Index: third_party/cython/src/Cython/Plex/Errors.py
diff --git a/third_party/cython/src/Cython/Plex/Errors.py b/third_party/cython/src/Cython/Plex/Errors.py
new file mode 100644
index 0000000000000000000000000000000000000000..891873b56feba2f951cd3ac0c97488eb7af1725a
--- /dev/null
+++ b/third_party/cython/src/Cython/Plex/Errors.py
@@ -0,0 +1,50 @@
+#=======================================================================
+#
+#   Python Lexical Analyser
+#
+#   Exception classes
+#
+#=======================================================================
+
+class PlexError(Exception):
+  message = ""
+
+class PlexTypeError(PlexError, TypeError):
+  pass
+
+class PlexValueError(PlexError, ValueError):
+  pass
+
+class InvalidRegex(PlexError):
+  pass
+
+class InvalidToken(PlexError):
+
+  def __init__(self, token_number, message):
+    PlexError.__init__(self, "Token number %d: %s" % (token_number, message))
+
+class InvalidScanner(PlexError):
+  pass
+
+class AmbiguousAction(PlexError):
+  message = "Two tokens with different actions can match the same string"
+
+  def __init__(self):
+    pass
+
+class UnrecognizedInput(PlexError):
+  scanner = None
+  position = None
+  state_name = None
+
+  def __init__(self, scanner, state_name):
+    self.scanner = scanner
+    self.position = scanner.get_position()
+    self.state_name = state_name
+
+  def __str__(self):
+    return ("'%s', line %d, char %d: Token not recognised in state %s"
+            % (self.position + (repr(self.state_name),)))
+
+
+