ERR: Raise ValueError with naive datetime and mixed UTC offsets
State: closed

- [x] closes #25978
- [x] tests added / passed
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [x] whatsnew entry


Labels:
name: Error Reporting
description: Incorrect or improved errors from pandas
name: Timezones
description: Timezone data dtype

Comments:
# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25982?src=pr&el=h1) Report
> Merging [#25982](https://codecov.io/gh/pandas-dev/pandas/pull/25982?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/1172d61aa8cb66e76af2bfdf8a70444802b28c6b?src=pr&el=desc) will **decrease** coverage by `<.01%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/25982/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/25982?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #25982      +/-   ##
==========================================
- Coverage   91.85%   91.84%   -0.01%     
==========================================
  Files         175      175              
  Lines       52554    52554              
==========================================
- Hits        48272    48268       -4     
- Misses       4282     4286       +4
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.4% <ø> (ø)` | :arrow_up: |
| #single | `41.91% <ø> (-0.08%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/25982?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/25982/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2dicS5weQ==) | `75% <0%> (-12.5%)` | :arrow_down: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/25982/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `96.79% <0%> (-0.12%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25982?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25982?src=pr&el=footer). Last update [1172d61...acd7128](https://codecov.io/gh/pandas-dev/pandas/pull/25982?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).

# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25982?src=pr&el=h1) Report
> Merging [#25982](https://codecov.io/gh/pandas-dev/pandas/pull/25982?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/70773d952bf52229d7214707ce6d66cee70607cb?src=pr&el=desc) will **decrease** coverage by `<.01%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/25982/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/25982?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #25982      +/-   ##
==========================================
- Coverage   91.86%   91.85%   -0.01%     
==========================================
  Files         175      175              
  Lines       52543    52543              
==========================================
- Hits        48267    48262       -5     
- Misses       4276     4281       +5
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.4% <ø> (ø)` | :arrow_up: |
| #single | `41.9% <ø> (-0.07%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/25982?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/25982/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2dicS5weQ==) | `75% <0%> (-12.5%)` | :arrow_down: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/25982/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `96.79% <0%> (-0.12%)` | :arrow_down: |
| [pandas/util/testing.py](https://codecov.io/gh/pandas-dev/pandas/pull/25982/diff?src=pr&el=tree#diff-cGFuZGFzL3V0aWwvdGVzdGluZy5weQ==) | `90.62% <0%> (-0.11%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25982?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25982?src=pr&el=footer). Last update [70773d9...b474f88](https://codecov.io/gh/pandas-dev/pandas/pull/25982?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).

Comments addressed and green. 
thanks @mroeschke