Reindexing two tz-aware (UTC) indices gives 'DatetimeArray subtraction must have the same timezones or no timezones'
#### Code Sample, a copy-pastable example if possible

```python
import pandas as pd
import datetime as dt

print(pd.__version__)
a = pd.date_range('2010-01-01', '2010-01-02', periods=24, tz='utc')
b = pd.date_range('2010-01-01', '2010-01-02', periods=23, tz='utc')
a.reindex(b, method='nearest', tolerance=dt.timedelta(seconds=20))
```
#### Problem description

Output is:
```
Python 3.7.4 (default, Jul 27 2019, 21:25:02) 
[GCC 7.4.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import pandas as pd
>>> import datetime as dt
>>> 
>>> print(pd.__version__)
1.0.2
>>> a = pd.date_range('2010-01-01', '2010-01-02', periods=24, tz='utc')
>>> b = pd.date_range('2010-01-01', '2010-01-02', periods=23, tz='utc')
>>> a.reindex(b, method='nearest', tolerance=dt.timedelta(seconds=20))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/andrew/project/ch2/choochoo-1/py/env/lib/python3.7/site-packages/pandas/core/indexes/base.py", line 3144, in reindex
    target, method=method, limit=limit, tolerance=tolerance
  File "/home/andrew/project/ch2/choochoo-1/py/env/lib/python3.7/site-packages/pandas/core/indexes/base.py", line 2740, in get_indexer
    indexer = self._get_nearest_indexer(target, limit, tolerance)
  File "/home/andrew/project/ch2/choochoo-1/py/env/lib/python3.7/site-packages/pandas/core/indexes/base.py", line 2830, in _get_nearest_indexer
    indexer = self._filter_indexer_tolerance(target, indexer, tolerance)
  File "/home/andrew/project/ch2/choochoo-1/py/env/lib/python3.7/site-packages/pandas/core/indexes/base.py", line 2834, in _filter_indexer_tolerance
    distance = abs(self.values[indexer] - target)
  File "/home/andrew/project/ch2/choochoo-1/py/env/lib/python3.7/site-packages/pandas/core/indexes/extension.py", line 147, in method
    result = meth(_maybe_unwrap_index(other))
  File "/home/andrew/project/ch2/choochoo-1/py/env/lib/python3.7/site-packages/pandas/core/arrays/datetimelike.py", line 1458, in __rsub__
    return -(self - other)
  File "/home/andrew/project/ch2/choochoo-1/py/env/lib/python3.7/site-packages/pandas/core/ops/common.py", line 64, in new_method
    return method(self, other)
  File "/home/andrew/project/ch2/choochoo-1/py/env/lib/python3.7/site-packages/pandas/core/arrays/datetimelike.py", line 1406, in __sub__
    result = self._sub_datetime_arraylike(other)
  File "/home/andrew/project/ch2/choochoo-1/py/env/lib/python3.7/site-packages/pandas/core/arrays/datetimes.py", line 667, in _sub_datetime_arraylike
    f"{type(self).__name__} subtraction must have the same "
TypeError: DatetimeArray subtraction must have the same timezones or no timezones
```

The problem is that I don't see how to reindex and / or the error message appears to be nonsensical since both have UTC timezones.

#### Expected Output

With 0.25.3 I see:
```
(DatetimeIndex([          '2010-01-01 00:00:00+00:00',
               '2010-01-01 01:05:27.272727272+00:00',
               '2010-01-01 02:10:54.545454545+00:00',
               '2010-01-01 03:16:21.818181818+00:00',
               '2010-01-01 04:21:49.090909090+00:00',
               '2010-01-01 05:27:16.363636363+00:00',
               '2010-01-01 06:32:43.636363636+00:00',
               '2010-01-01 07:38:10.909090909+00:00',
               '2010-01-01 08:43:38.181818181+00:00',
               '2010-01-01 09:49:05.454545454+00:00',
               '2010-01-01 10:54:32.727272727+00:00',
                         '2010-01-01 12:00:00+00:00',
               '2010-01-01 13:05:27.272727272+00:00',
               '2010-01-01 14:10:54.545454545+00:00',
               '2010-01-01 15:16:21.818181818+00:00',
               '2010-01-01 16:21:49.090909090+00:00',
               '2010-01-01 17:27:16.363636363+00:00',
               '2010-01-01 18:32:43.636363636+00:00',
               '2010-01-01 19:38:10.909090909+00:00',
               '2010-01-01 20:43:38.181818181+00:00',
               '2010-01-01 21:49:05.454545454+00:00',
               '2010-01-01 22:54:32.727272727+00:00',
                         '2010-01-02 00:00:00+00:00'],
              dtype='datetime64[ns, UTC]', freq=None), array([ 0, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
       -1, -1, -1, -1, -1, 23]))
```

#### Output of ``pd.show_versions()``

<details>

[paste the output of ``pd.show_versions()`` here below this line]
INSTALLED VERSIONS
------------------
commit           : None
python           : 3.7.4.final.0
python-bits      : 64
OS               : Linux
OS-release       : 4.12.14-lp151.28.36-default
machine          : x86_64
processor        : x86_64
byteorder        : little
LC_ALL           : None
LANG             : en_GB.UTF-8
LOCALE           : en_GB.UTF-8

pandas           : 1.0.2
numpy            : 1.18.1
pytz             : 2019.3
dateutil         : 2.8.1
pip              : 20.0.2
setuptools       : 40.8.0
Cython           : None
pytest           : None
hypothesis       : None
sphinx           : None
blosc            : None
feather          : None
xlsxwriter       : None
lxml.etree       : None
html5lib         : None
pymysql          : None
psycopg2         : None
jinja2           : 2.11.1
IPython          : 7.13.0
pandas_datareader: None
bs4              : None
bottleneck       : None
fastparquet      : None
gcsfs            : None
lxml.etree       : None
matplotlib       : 3.2.0
numexpr          : None
odfpy            : None
openpyxl         : 3.0.3
pandas_gbq       : None
pyarrow          : None
pytables         : None
pytest           : None
pyxlsb           : None
s3fs             : None
scipy            : 1.4.1
sqlalchemy       : 1.3.15
tables           : None
tabulate         : None
xarray           : None
xlrd             : None
xlwt             : None
xlsxwriter       : None
numba            : None
</details>
