Dataframe.plot  error (on version 0.25.1)
#### Code Sample, a copy-pastable example if possible

```python
# Your code here
import pandas as pd
import numpy as np
import matplotlib.pyplot as plt
da = np.arange(12).reshape(6,2)
df=pd.DataFrame(da,columns=list('ab'))
fig, ax = plt.subplots()
df[['a']].plot(x=df['b'],ax=ax)
plt.show()
```
#### Problem description
these test code run ok on pandas version 0.20.0 ,but error on pandas version is 0.25.1.
the error info is:
KeyError: "None of [Int64Index([1, 3, 5, 7, 9, 11], dtype='int64')] are in the [columns]"

the detail trace info are:

File "E:/pytest/dfplot1.py", line 7, in 
df[['a']].plot(x=df['b'],ax=ax)
File "C:\Program Files\Python37\lib\site-packages\pandas\plotting_core.py", line 759, in call
elif not isinstance(data[x], ABCSeries):
File "C:\Program Files\Python37\lib\site-packages\pandas\core\frame.py", line 2986, in getitem
indexer = self.loc._convert_to_indexer(key, axis=1, raise_missing=True)
File "C:\Program Files\Python37\lib\site-packages\pandas\core\indexing.py", line 1285, in _convert_to_indexer
return self._get_listlike_indexer(obj, axis, **kwargs)[1]
File "C:\Program Files\Python37\lib\site-packages\pandas\core\indexing.py", line 1092, in _get_listlike_indexer
keyarr, indexer, o._get_axis_number(axis), raise_missing=raise_missing
File "C:\Program Files\Python37\lib\site-packages\pandas\core\indexing.py", line 1177, in _validate_read_indexer
key=key, axis=self.obj._get_axis_name(axis)
KeyError: "None of [Int64Index([1, 3, 5, 7, 9, 11], dtype='int64')] are in the [columns]"

[this should explain **why** the current behaviour is a problem and why the expected output is a better solution.]

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#### Expected Output

#### 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               : Windows
OS-release       : 7
machine          : AMD64
processor        : Intel64 Family 6 Model 60 Stepping 3, GenuineIntel
byteorder        : little
LC_ALL           : None
LANG             : None
LOCALE           : None.None
pandas           : 0.25.1
numpy            : 1.17.2
pytz             : 2019.2
dateutil         : 2.8.0
pip              : 19.0.3
setuptools       : 40.8.0
Cython           : None
pytest           : None
hypothesis       : None
sphinx           : None
blosc            : None
feather          : None
xlsxwriter       : None
lxml.etree       : None
html5lib         : None
pymysql          : 0.9.3
psycopg2         : None
jinja2           : None
IPython          : None
pandas_datareader: None
bs4              : None
bottleneck       : None
fastparquet      : None
gcsfs            : None
lxml.etree       : None
matplotlib       : 3.1.1
numexpr          : None
odfpy            : None
openpyxl         : None
pandas_gbq       : None
pyarrow          : None
pytables         : None
s3fs             : None
scipy            : None
sqlalchemy       : 1.3.8
tables           : None
xarray           : None
xlrd             : None
xlwt             : None
xlsxwriter       : None

</details>
