"email.errors"：例外和缺陷類別
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**原始碼：**Lib/email/errors.py

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

exception email.errors.MessageError

   This is the base class for all exceptions that the "email" package
   can raise.  It is derived from the standard "Exception" class and
   defines no additional methods.

exception email.errors.MessageParseError

   This is the base class for exceptions raised by the "Parser" class.
   It is derived from "MessageError".  This class is also used
   internally by the parser used by "headerregistry".

exception email.errors.HeaderParseError

   Raised under some error conditions when parsing the **RFC 5322**
   headers of a message, this class is derived from
   "MessageParseError".  The "set_boundary()" method will raise this
   error if the content type is unknown when the method is called.
   "Header" may raise this error for certain base64 decoding errors,
   and when an attempt is made to create a header that appears to
   contain an embedded header (that is, there is what is supposed to
   be a continuation line that has no leading whitespace and looks
   like a header).

exception email.errors.BoundaryError

   Deprecated and no longer used.

exception email.errors.MultipartConversionError

   Raised if the "attach()" method is called on an instance of a class
   derived from "MIMENonMultipart" (e.g. "MIMEImage").
   "MultipartConversionError" multiply inherits from "MessageError"
   and the built-in "TypeError".

exception email.errors.HeaderWriteError

   Raised when an error occurs when the "generator" outputs headers.

exception email.errors.MessageDefect

   This is the base class for all defects found when parsing email
   messages. It is derived from "ValueError".

exception email.errors.HeaderDefect

   This is the base class for all defects found when parsing email
   headers. It is derived from "MessageDefect".

Here is the list of the defects that the "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 *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 "email.errors.MessageDefect".

exception email.errors.NoBoundaryInMultipartDefect

   A message claimed to be a multipart, but had no *boundary*
   parameter.

exception email.errors.StartBoundaryNotFoundDefect

   The start boundary claimed in the *Content-Type* header was never
   found.

exception email.errors.CloseBoundaryNotFoundDefect

   A start boundary was found, but no corresponding close boundary was
   ever found.

   在 3.3 版被加入.

exception email.errors.FirstHeaderLineIsContinuationDefect

   The message had a continuation line as its first header line.

exception email.errors.MisplacedEnvelopeHeaderDefect

   A "Unix From" header was found in the middle of a header block.

exception email.errors.MissingHeaderBodySeparatorDefect

   A line was found while parsing headers that had no leading white
   space but contained no ':'.  Parsing continues assuming that the
   line represents the first line of the body.

   在 3.3 版被加入.

exception email.errors.MalformedHeaderDefect

   A header was found that was missing a colon, or was otherwise
   malformed.

   在 3.3 版之後被棄用: This defect has not been used for several
   Python versions.

exception email.errors.MultipartInvariantViolationDefect

   A message claimed to be a *multipart*, but no subparts were found.
   Note that when a message has this defect, its "is_multipart()"
   method may return "False" even though its content type claims to be
   *multipart*.

exception email.errors.InvalidBase64PaddingDefect

   When decoding a block of base64 encoded bytes, the padding was not
   correct. Enough padding is added to perform the decode, but the
   resulting decoded bytes may be invalid.

exception email.errors.InvalidBase64CharactersDefect

   When decoding a block of base64 encoded bytes, characters outside
   the base64 alphabet were encountered.  The characters are ignored,
   but the resulting decoded bytes may be invalid.

exception email.errors.InvalidBase64LengthDefect

   When decoding a block of base64 encoded bytes, the number of non-
   padding base64 characters was invalid (1 more than a multiple of
   4).  The encoded block was kept as-is.

exception email.errors.InvalidDateDefect

   When decoding an invalid or unparsable date field.  The original
   value is kept as-is.
