error: Fix super calls for SMTPAuthenticationError, etc.

Fix copy/paste errors where super() calls used the wrong class name
(it should match the class in which the method is defined) for:

* SMTPAuthenticationError.__init__
* ProcessingError.__init__
* OPMLReadError.__init__

Reported-by: Matt Bordignon <matthew@bordignons.net>
Signed-off-by: W. Trevor King <wking@tremily.us>
feed: Catch parsing errors during html2text

This avoids crashing with:

  Traceback (most recent call last):
    ...
    File ".../rss2email/feed.py", line 732, in _process_entry_content
      lines = [_html2text.html2text(content['value'])]
    ...
    File "/usr/lib/python3.2/html/parser.py", line 149, in error
      raise HTMLParseError(message, self.getpos())
  html.parser.HTMLParseError: EOF in middle of construct, at line 1, column 262

The troublesome feed was:

  $ wget -S http://www.cell.com/rssFeed/biophysj/rss.NewIssueAndArticles.xml
  --2013-03-20 05:22:08--  http://www.cell.com/rssFeed/biophysj/rss.NewIssueAndArticles.xml
  Resolving www.cell.com... 145.36.42.28
  Connecting to www.cell.com|145.36.42.28|:80... connected.
  HTTP request sent, awaiting response...
    HTTP/1.1 200 OK
    Date: Wed, 20 Mar 2013 09:23:19 GMT
    Server: IBM_HTTP_Server
    Last-Modified: Tue, 19 Mar 2013 22:00:04 GMT
    Accept-Ranges: bytes
    Content-Length: 15362
    Vary: Accept-Encoding
    Keep-Alive: timeout=10, max=100
    Connection: Keep-Alive
    Content-Type: text/xml
  Length: 15362 (15K) [text/xml]
  Saving to: ‘rss.NewIssueAndArticles.xml’

  100%[======================================>] 15,362      94.1KB/s   in 0.2s

  2013-03-20 05:22:08 (94.1 KB/s) - ‘rss.NewIssueAndArticles.xml’ saved [15362/15362]

which contained the poorly split summary:

  <item>
    <title>Synergistic Insertion of Antimicrobial Magainin-Family Peptides in Membranes Depends on the Lipid Spontaneous Curvature</title>
    <link>http://www.cell.com/biophysj/abstract/S0006-3495(13)00153-7</link>
    <description>Erik Strandberg, Jonathan Zerweck, Parvesh Wadhwani, Anne S. Ulrich. PGLa and magainin 2 (MAG2) are amphiphilic antimicrobial peptides from frog skin with known synergistic activity. The orientation of the two helices in membranes was studied using solid-state &lt;sup....</description>
    <pubDate>Tue, 19 Mar 2013 00:00:00 GMT</pubDate>
    <guid>http://www.cell.com/biophysj/abstract/S0006-3495(13)00153-7</guid>
    <dc:date>2013-03-19T00:00:00Z</dc:date>
  </item>

The '<sup....' in the description broke the parser.

Signed-off-by: W. Trevor King <wking@tremily.us>
error: Fix ProcessingError message and logging

We can't check if message is None if message wasn't an argument to
__init__().  Also:

* import sys for sys.version
* explicitly format strings passed to _LOG.warning(), otherwise you'll
  get the following:

    >>> LOG.warning('abc', 'def')
    Traceback (most recent call last):
      ...
    TypeError: not all arguments converted during string formatting

Signed-off-by: W. Trevor King <wking@tremily.us>
feed: Add herror to _SOCKET_ERRORS and remove reason handing

We don't log the reason, so trying to extract it just gives room for
errors to creep in.  Luckily, we'll be able to drop the whole
_SOCKET_ERRORS thing when we move to Python >= 3.3, because following
PEP 3151 the socket errors became subclasses of OSError.

Reported-by: Matt Bordignon <matthew@bordignons.net>
Signed-off-by: W. Trevor King <wking@tremily.us>