Different results with tzlib and dateutil_tz with "ambiguous" argument to tz_localize

[toobaz]

Code Sample, a copy-pastable example if possible

In [2]: import pytz

In [3]: pytz_tz = pytz.timezone('US/Eastern')
   ...: dateutil_tz = pd._libs.tslib.maybe_get_tz('dateutil/US/Eastern')
   ...: 

In [4]: idx = pd.DatetimeIndex(['2011-11-06 01:00:00'])

In [5]: l1 = idx.tz_localize(pytz_tz, ambiguous=[1])

In [6]: l2 = idx.tz_localize(dateutil_tz, ambiguous=[1])

In [7]: l1 == l2
Out[7]: array([ True], dtype=bool)

In [8]: l1[0] == l2[0]
Out[8]: True

In [9]: str(l1[0]) == str(l2[0])
Out[9]: False

In [10]: l1, l2
Out[10]: 
(DatetimeIndex(['2011-11-06 01:00:00-04:00'], dtype='datetime64[ns, US/Eastern]', freq=None),
 DatetimeIndex(['2011-11-06 01:00:00-05:00'], dtype='datetime64[ns, tzfile('/usr/share/zoneinfo/US/Eastern')]', freq=None))

Problem description

I guess (and the existing tests suggest) the two should produce the same results.

Expected Output

l1 and l2 should be perfectly equivalent I guess.

Output of pd.show_versions()

INSTALLED VERSIONS ------------------ commit: 1002cc3 python: 3.5.3.final.0 python-bits: 64 OS: Linux OS-release: 4.7.0-1-amd64 machine: x86_64 processor: byteorder: little LC_ALL: None LANG: it_IT.utf8 LOCALE: it_IT.UTF-8

pandas: 0.20.0rc1+53.g1002cc339
pytest: 3.0.6
pip: 9.0.1
setuptools: 33.1.1
Cython: 0.25.2
numpy: 1.12.1
scipy: 0.18.1
xarray: 0.9.1
IPython: 5.1.0.dev
sphinx: 1.4.9
patsy: 0.3.0-dev
dateutil: 2.5.3
pytz: 2016.7
blosc: None
bottleneck: 1.2.0
tables: 3.3.0
numexpr: 2.6.1
feather: 0.3.1
matplotlib: 2.0.0
openpyxl: 2.3.0
xlrd: 1.0.0
xlwt: 1.1.2
xlsxwriter: 0.9.6
lxml: 3.7.1
bs4: 4.5.3
html5lib: 0.999999999
sqlalchemy: 1.0.15
pymysql: None
psycopg2: None
jinja2: 2.8
s3fs: None
pandas_gbq: None
pandas_datareader: 0.2.1

[jreback]

no, these are not equivalent in reality. yes in theory they should be but I doubt that there is actual equivalence between these different timezone databases. nor do we actually care. you can either use one or the other. anything else would be way too complicated.

if you want to offer a doc note somewhere I guess that would be ok.