BUG: with integer column labels, .info() throws KeyError after column subsetting with .loc[]
- [x] I have checked that this issue has not already been reported.

- [x] I have confirmed this bug exists on the latest version of pandas.

- [ ] (optional) I have confirmed this bug exists on the master branch of pandas.

---

**Note**: Please read [this guide](https://matthewrocklin.com/blog/work/2018/02/28/minimal-bug-reports) detailing how to provide the necessary information for us to reproduce your bug.

#### Code Sample, a copy-pastable example

```python
import numpy as np
import pandas as pd

df = pd.DataFrame(np.random.random(size=(2, 3)),
                  index=['A', 'B'],
                  columns=[0, 1, 2])

print(df.info())
<class 'pandas.core.frame.DataFrame'>
Index: 2 entries, A to B
Data columns (total 3 columns):
 #   Column  Non-Null Count  Dtype  
---  ------  --------------  -----  
 0   0       2 non-null      float64
 1   1       2 non-null      float64
 2   2       2 non-null      float64
dtypes: float64(3)
memory usage: 64.0+ bytes
None

print(df.loc[:, [1, 2]])
          1         2
A  0.950714  0.731994
B  0.156019  0.155995

print(df.loc[:, [1, 2]].info())
Traceback (most recent call last):
  File ".../.pyenv/versions/dm/lib/python3.8/site-packages/pandas/core/indexes/base.py", line 2895, in get_loc
    return self._engine.get_loc(casted_key)
  File "pandas/_libs/index.pyx", line 70, in pandas._libs.index.IndexEngine.get_loc
  File "pandas/_libs/index.pyx", line 101, in pandas._libs.index.IndexEngine.get_loc
  File "pandas/_libs/hashtable_class_helper.pxi", line 1032, in pandas._libs.hashtable.Int64HashTable.get_item
  File "pandas/_libs/hashtable_class_helper.pxi", line 1039, in pandas._libs.hashtable.Int64HashTable.get_item
KeyError: 0

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "some_file.py", line 32, in <module>
    print(df.loc[:, [1, 2]].info())
  File ".../.pyenv/versions/dm/lib/python3.8/site-packages/pandas/core/frame.py", line 2589, in info
    return DataFrameInfo(
  File ".../.pyenv/versions/dm/lib/python3.8/site-packages/pandas/io/formats/info.py", line 250, in info
    self._verbose_repr(lines, ids, dtypes, show_counts)
  File ".../.pyenv/versions/dm/lib/python3.8/site-packages/pandas/io/formats/info.py", line 335, in _verbose_repr
    dtype = dtypes[i]
  File ".../.pyenv/versions/dm/lib/python3.8/site-packages/pandas/core/series.py", line 882, in __getitem__
    return self._get_value(key)
  File ".../.pyenv/versions/dm/lib/python3.8/site-packages/pandas/core/series.py", line 989, in _get_value
    loc = self.index.get_loc(label)
  File ".../.pyenv/versions/dm/lib/python3.8/site-packages/pandas/core/indexes/base.py", line 2897, in get_loc
    raise KeyError(key) from err
KeyError: 0

Process finished with exit code 1
```

#### Problem description
When column names are integers, calling `.info()` after selecting a subset of the columns using `.loc[:, [...]]` causes the above error.

Converting to `str` avoids the error:
```
df.columns = df.columns.astype(str)
print(df.loc[:, ['1', '2']].info())

<class 'pandas.core.frame.DataFrame'>
Index: 2 entries, A to B
Data columns (total 2 columns):
 #   Column  Non-Null Count  Dtype  
---  ------  --------------  -----  
 0   1       2 non-null      float64
 1   2       2 non-null      float64
dtypes: float64(2)
memory usage: 48.0+ bytes
None
```

#### Expected Output
Standard `.info()` DataFrame summary.

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

<details>

INSTALLED VERSIONS
------------------
commit           : db08276bc116c438d3fdee492026f8223584c477
python           : 3.8.5.final.0
python-bits      : 64
OS               : Linux
OS-release       : 5.4.0-51-generic
Version          : #56-Ubuntu SMP Mon Oct 5 14:28:49 UTC 2020
machine          : x86_64
processor        : x86_64
byteorder        : little
LC_ALL           : None
LANG             : en_US.UTF-8
LOCALE           : en_US.UTF-8

pandas           : 1.1.3
numpy            : 1.19.2
pytz             : 2020.1
dateutil         : 2.8.1
pip              : 20.2.3
setuptools       : 50.3.0
Cython           : None
pytest           : None
hypothesis       : None
sphinx           : None
blosc            : None
feather          : None
xlsxwriter       : None
lxml.etree       : 4.5.2
html5lib         : None
pymysql          : None
psycopg2         : None
jinja2           : 2.11.2
IPython          : 7.18.1
pandas_datareader: None
bs4              : None
bottleneck       : None
fsspec           : 0.8.3
fastparquet      : 0.4.1
gcsfs            : 0.7.1
matplotlib       : 3.3.2
numexpr          : 2.7.1
odfpy            : None
openpyxl         : 3.0.5
pandas_gbq       : None
pyarrow          : 1.0.1
pytables         : None
pyxlsb           : None
s3fs             : None
scipy            : 1.5.2
sqlalchemy       : None
tables           : 3.6.1
tabulate         : None
xarray           : None
xlrd             : 1.2.0
xlwt             : None
numba            : 0.51.2
None]

</details>
