BUG: Append DataFrame to Series with dateutil timezone
- [x] closes #23682
- [x] tests added / passed
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [x] whatsnew entry

Hello @mroeschke! Thanks for submitting the PR.

 - There are no PEP8 issues in the file [`pandas/tests/reshape/test_concat.py`](https://github.com/mroeschke/pandas/blob/850aaf9da0a5679847dac2c93d16ab70bf2b7533/pandas/tests/reshape/test_concat.py) !

 Failure on the py2 build:

```
________ TestAppend.test_append_empty_frame_to_series_with_dateutil_tz _________
[gw0] linux2 -- Python 2.7.15 /home/travis/miniconda3/envs/pandas/bin/python
self = <pandas.tests.reshape.test_concat.TestAppend object at 0x7fa55d3e2390>
    def test_append_empty_frame_to_series_with_dateutil_tz(self):
        # GH 23682
>       date = Timestamp('2018-10-24 07:30:00', tz=dateutil.tz.UTC)
E       AttributeError: 'module' object has no attribute 'UTC'
```

I think that's using `python-dateutil=2.5.0` # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/23685?src=pr&el=h1) Report
> Merging [#23685](https://codecov.io/gh/pandas-dev/pandas/pull/23685?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/e413c491e090274aad78489cc17a2e29cbd8e269?src=pr&el=desc) will **not change** coverage.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/23685/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/23685?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master   #23685   +/-   ##
=======================================
  Coverage   92.24%   92.24%           
=======================================
  Files         161      161           
  Lines       51339    51339           
=======================================
  Hits        47360    47360           
  Misses       3979     3979
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.64% <ø> (ø)` | :arrow_up: |
| #single | `42.34% <ø> (ø)` | :arrow_up: |


------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/23685?src=pr&el=continue).
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> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/23685?src=pr&el=footer). Last update [e413c49...5d563aa](https://codecov.io/gh/pandas-dev/pandas/pull/23685?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 can you merge master Done thanks!