remove local iso8601 and use pypi version

When running some tests on another project I stumbled upon a failed
test that revealed a bug in colander's iso8601.  If you try to
deserialize "2014-09-09T15:15:57.516967" into a datetime object you
get `datetime.datetime(2014, 9, 9, 15, 15, 57, 516966)` (notice the
microseconds are off by 1).  I traced it down to this:

```
groups["fraction"] = int(float("0.%s" % groups["fraction"]) * 1e6)
```

`int(float("0.%s" % "516967") * 1e6)` is equal to 516966 due to
rounding.

I was going to fix it, but iso8601 is a currently maintained project
on pypi that has this issue (and possibly others) already fixed.
So, it makes much more sense to offload everything back to that project.

The only difference (besides the bug fixes) is following:

`iso8601.Utc` => `iso8601.iso8601.Utc`
`iso8601.FixedOffset` => `iso8601.iso8601.FixedOffset`

colander/iso8601.py

@@ -1,152 +1,4 @@
-"""
-Copyright (c) 2007 Michael Twomey
-
-Permission is hereby granted, free of charge, to any person obtaining a
-copy of this software and associated documentation files (the
-"Software"), to deal in the Software without restriction, including
-without limitation the rights to use, copy, modify, merge, publish,
-distribute, sublicense, and/or sell copies of the Software, and to
-permit persons to whom the Software is furnished to do so, subject to
-the following conditions:
-
-The above copyright notice and this permission notice shall be included
-in all copies or substantial portions of the Software.
-
-THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
-OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
-MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
-IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
-CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
-TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
-SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
-
-ISO 8601 date time string parsing
-
-Basic usage:
->>> import iso8601
->>> iso8601.parse_date("2007-01-25T12:00:00Z")
-datetime.datetime(2007, 1, 25, 12, 0, tzinfo=<iso8601.iso8601.Utc ...>)
->>>
-"""
-
-
-from datetime import datetime, timedelta, tzinfo
-import re
-
-from .compat import string_types
+import iso8601
+from iso8601.iso8601 import (parse_date, ParseError, Utc, FixedOffset, UTC, ZERO)
 
 __all__ = ["parse_date", "ParseError", "Utc", "FixedOffset"]
-
-# Adapted from http://delete.me.uk/2005/03/iso8601.html
-ISO8601_REGEX = re.compile(
-    r"(?P<year>[0-9]{4})(-(?P<month>[0-9]{1,2})(-(?P<day>[0-9]{1,2})"
-    r"((?P<separator>.)(?P<hour>[0-9]{2})(:(?P<minute>[0-9]{2})(:(?P<second>[0-9]{2})(\.(?P<fraction>[0-9]+))?)?)?"
-    r"(?P<timezone>Z|(([-+])([0-9]{2})(:?([0-9]{2}))?))?)?)?)?"
-)
-TIMEZONE_REGEX = re.compile(
-    "(?P<prefix>[+-])(?P<hours>[0-9]{2})(:?(?P<minutes>[0-9]{2}))?")
-
-class ParseError(Exception):
-    """Raised when there is a problem parsing a date string"""
-
-# Yoinked from python docs
-ZERO = timedelta(0)
-class Utc(tzinfo):
-    """UTC
-
-    """
-    def utcoffset(self, dt):
-        return ZERO
-
-    def tzname(self, dt):
-        return "UTC"
-
-    def dst(self, dt):
-        return ZERO
-UTC = Utc()
-
-class FixedOffset(tzinfo):
-    """Fixed offset in hours and minutes from UTC
-
-    """
-    def __init__(self, offset_hours, offset_minutes, name):
-        self.__offset = timedelta(hours=offset_hours, minutes=offset_minutes)
-        self.__name = name
-
-    def __getinitargs__(self):
-        # tzinfo.__reduce__ returns the type as the factory:  supply
-        # defaults here, rather than in __init__.
-        return 0, 0, 'unknown'
-
-    def utcoffset(self, dt):
-        return self.__offset
-
-    def tzname(self, dt):
-        return self.__name
-
-    def dst(self, dt):
-        return ZERO
-
-    def __repr__(self):
-        return "<FixedOffset %r>" % self.__name
-
-def parse_timezone(tzstring, default_timezone=UTC):
-    """Parses ISO 8601 time zone specs into tzinfo offsets
-
-    """
-    if tzstring == "Z":
-        return UTC
-    # This isn't strictly correct, but it's common to encounter dates without
-    # timezones so I'll assume the default (which defaults to UTC).
-    # Addresses issue 4.
-    if tzstring is None:
-        return default_timezone
-    m = TIMEZONE_REGEX.match(tzstring)
-    prefix = m.group('prefix')
-    hours = int(m.group('hours'))
-    minutes = m.group('minutes')
-    if minutes is None:
-        minutes = 0
-    else:
-        minutes = int(minutes)
-    if prefix == "-":
-        hours = -hours
-        minutes = -minutes
-    return FixedOffset(hours, minutes, tzstring)
-
-def parse_date(datestring, default_timezone=UTC):
-    """Parses ISO 8601 dates into datetime objects
-
-    The timezone is parsed from the date string. However it is quite common to
-    have dates without a timezone (not strictly correct). In this case the
-    default timezone specified in default_timezone is used. This is UTC by
-    default.
-    """
-    if not isinstance(datestring, string_types):
-        raise ParseError("Expecting a string %r" % datestring)
-    m = ISO8601_REGEX.match(datestring)
-    if not m:
-        raise ParseError("Unable to parse date string %r" % datestring)
-    groups = m.groupdict()
-    tz = parse_timezone(groups["timezone"], default_timezone=default_timezone)
-    if (groups['year'] is None or
-        groups['month'] is None or
-        groups['day'] is None):
-        raise ParseError('Unable to parse date string %r' % datestring)
-    if groups["hour"] is None:
-        groups["hour"] = 0
-    if groups["minute"] is None:
-        groups["minute"] = 0
-    if groups["second"] is None:
-        groups["second"] = 0
-    if groups["fraction"] is None:
-        groups["fraction"] = 0
-    else:
-        groups["fraction"] = int(float("0.%s" % groups["fraction"]) * 1e6)
-    try:
-        return datetime(
-            int(groups["year"]), int(groups["month"]), int(groups["day"]),
-            int(groups["hour"]), int(groups["minute"]), int(groups["second"]),
-            int(groups["fraction"]), tz)
-    except ValueError as e:
-        raise ParseError(*e.args)

colander/tests/test_iso8601.py

@@ -68,12 +68,17 @@ def test_picklability(self):
     def test___repr__(self):
         inst = self._makeOne()
         result = inst.__repr__()
-        self.assertEqual(result, "<FixedOffset 'oneandahalf'>")
+        self.assertEqual(result, "<FixedOffset 'oneandahalf' datetime.timedelta(0, 5400)>")
 
 class Test_parse_timezone(unittest.TestCase):
     def _callFUT(self, tzstring, **kw):
-        from ..iso8601 import parse_timezone
-        return parse_timezone(tzstring, **kw)
+        # mimic old parse_timezone() by returning a FixedOffset
+        from datetime import tzinfo
+        from ..iso8601 import (parse_date, FixedOffset)
+        if tzstring is None:
+            tzstring = ''
+        dt = parse_date("2006-10-11T00:14:33{}".format(tzstring), **kw)
+        return dt.tzinfo
 
     def test_default_Z(self):
         from ..iso8601 import UTC

setup.py

@@ -30,7 +30,7 @@ def read(fname):
     README = ''
     CHANGES = ''
 
-requires = ['translationstring']
+requires = ['translationstring', 'iso8601']
 
 testing_extras = ['nose', 'coverage']
 docs_extras = ['Sphinx']