:mod:`email`: Exception and Defect classes

------------------------------------------

.. module:: email.errors

   :synopsis: The exception classes used by the email package.

The following exception classes are defined in the :mod:`email.errors` module:

.. exception:: MessageError()

   This is the base class for all exceptions that the :mod:`email` package can

   raise.  It is derived from the standard :exc:`Exception` class and defines no

   additional methods.

.. exception:: MessageParseError()

   This is the base class for exceptions thrown by the :class:`Parser` class.  It

   is derived from :exc:`MessageError`.

.. exception:: HeaderParseError()

   Raised under some error conditions when parsing the :rfc:`2822` headers of a

   message, this class is derived from :exc:`MessageParseError`. It can be raised

   from the :meth:`Parser.parse` or :meth:`Parser.parsestr` methods.

   Situations where it can be raised include finding an envelope header after the

   first :rfc:`2822` header of the message, finding a continuation line before the

   first :rfc:`2822` header is found, or finding a line in the headers which is

   neither a header or a continuation line.

.. exception:: BoundaryError()

   Raised under some error conditions when parsing the :rfc:`2822` headers of a

   message, this class is derived from :exc:`MessageParseError`. It can be raised

   from the :meth:`Parser.parse` or :meth:`Parser.parsestr` methods.

   Situations where it can be raised include not being able to find the starting or

   terminating boundary in a :mimetype:`multipart/\*` message when strict parsing

   is used.

.. exception:: MultipartConversionError()

   Raised when a payload is added to a :class:`Message` object using

   :meth:`add_payload`, but the payload is already a scalar and the message's

   :mailheader:`Content-Type` main type is not either :mimetype:`multipart` or

   missing.  :exc:`MultipartConversionError` multiply inherits from

   :exc:`MessageError` and the built-in :exc:`TypeError`.

   Since :meth:`Message.add_payload` is deprecated, this exception is rarely raised

   in practice.  However the exception may also be raised if the :meth:`attach`

   method is called on an instance of a class derived from

   :class:`MIMENonMultipart` (e.g. :class:`MIMEImage`).

Here's the list of the defects that the :class:`FeedParser` can find while

parsing messages.  Note that the defects are added to the message where the

problem was found, so for example, if a message nested inside a

:mimetype:`multipart/alternative` had a malformed header, that nested message

object would have a defect, but the containing messages would not.

All defect classes are subclassed from :class:`email.errors.MessageDefect`, but

this class is *not* an exception!

.. versionadded:: 2.4

   All the defect classes were added.

* :class:`NoBoundaryInMultipartDefect` -- A message claimed to be a multipart,

  but had no :mimetype:`boundary` parameter.

* :class:`StartBoundaryNotFoundDefect` -- The start boundary claimed in the

  :mailheader:`Content-Type` header was never found.

* :class:`FirstHeaderLineIsContinuationDefect` -- The message had a continuation

  line as its first header line.

* :class:`MisplacedEnvelopeHeaderDefect` - A "Unix From" header was found in the

  middle of a header block.

* :class:`MalformedHeaderDefect` -- A header was found that was missing a colon,

  or was otherwise malformed.

* :class:`MultipartInvariantViolationDefect` -- A message claimed to be a

  :mimetype:`multipart`, but no subparts were found.  Note that when a message has

  this defect, its :meth:`is_multipart` method may return false even though its

  content type claims to be :mimetype:`multipart`.