Fix unrecognized 'Z' UTC designator
closes [#8771](https://github.com/pydata/pandas/issues/8771)

ok, looks simple enough! cross-fingers other tests pass!
pls add a release note as well (referencing the original issue) (put in bug-fixes, though you can say regression)
 Hi, do you need me to do other modifications before merging? Let me know
 looks good. pls rebase and squash. ping when green.
 done!
 merged via https://github.com/pydata/pandas/commit/c03e92f4e3c1ab978b3111556019a502ae55f1e4
 @broessli hmm, I think this was changed before the latest travis build. Thought it was green.

Can you see what the problem is and and do a follow up PR? thanks (pls submit a new PR, can't push to this one anymore)

https://travis-ci.org/pydata/pandas/builds/41039139
 Yes, sorry about that. The issue seems related to `dateutil` behavior, which is the fallback when parsing dates with `...Z00`, depending on the version we can get a time zone equal to tzutc() or tzlocal(). Not sure how to handle this (besides dropping the test on `Z00`...)
 By the way, checking ISO 8601 I am not sure what to expect exactly with `Z00`, is it really legit?
 so it give one answer on dateutil 1.5 and a different on 2.1/2.2?

you can do the test like this:

```
from distutils.version import LooseVersion

.....


if LooseVersion(dateutil.__version__) >= '2.2':
    #.....
else:
    # ....
```

I am not sure of the defined behavior of `...Z00`

cc @rockg ?
 Actually, testing on my machine, I always get `tzutc()` regardless of `dateutil`'s version, cannot figure out why this is different on Travis 
 hmm, I think this might have to do with the cache not updating because only the .c files were changed (and not the cython files). let me see.
 reverted for now: https://github.com/pydata/pandas/commit/6f48d4a18cf92ffaceff3f6c53766004895194c9

got ahead and rebase on master and put up a new PR (close this one)
 cc @dbew  

any thoughts on the above? 

https://travis-ci.org/pydata/pandas/builds/41039139
 Nothing jumps out, I'm afraid.

There were definitely differences between python 3 and python 2 when I did the original dateutil work but the issues I had were all around UTC and the implementation of the timezones, not tzlocal and parsing. 

Looking at the parse code in dateutil, I think it reads the timezone name and first tests if it matches the local timezone (`tzname in time.tzname`) then tests if it matches UTC - so if 'Z' matches the local timezone then it wouldn't be reported at UTC.
