Pandas 1.0.1 gives 1953 TypeError: Cannot use .str.encode with values of inferred dtype 'bytes'.
#### Code Sample, a copy-pastable example if possible
This code is used in jupyter lab using python 3.7 and pandas 1.0.1
It accesses a text file of words delimited by carriage returns
```
import base64
import numpy as np
import pandas as pd
words = pd.read_table("sampleTEXT.txt",names=['word'],header=None)
words.head()
---   word
--0  difference
--1  where
--2  mc
--3  is
--4  the
words['word_encoded'] = words.word.str.encode('utf-8', 'strict').str.encode('base64')

```


#### Problem description
the following error appears:
```
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-4-0f7040aa4d4e> in <module>
----> 1 words['word_encoded'] = words.word.str.encode('utf-8', 'strict').str.encode('base64')

~/miniconda3/envs/p37cu10.2PyTo/lib/python3.7/site-packages/pandas/core/strings.py in wrapper(self, *args, **kwargs)
   1949                     f"inferred dtype '{self._inferred_dtype}'."
   1950                 )
-> 1951                 raise TypeError(msg)
   1952             return func(self, *args, **kwargs)
   1953 

TypeError: Cannot use .str.encode with values of inferred dtype 'bytes'.
```

#### Expected Output
If I downgrade pandas to '0.24.2' then I get the desired output
```
       word                  word_encoded
-----------------------------------------------------
0      difference           b'ZGlmZmVyZW5jZQ==\n'
1      where                 b'd2hlcmU=\n'
2      mc                      b'bWM=\n'
3      is                        b'aXM=\n'
4      the                      b'dGhl\n'
```
I discussed this problem on stackoverflow here

https://stackoverflow.com/questions/60254107/how-to-base64-encode-and-decode-a-column-in-python-pandas/60254651?noredirect=1#comment106581486_6025465

I read here
https://pandas.pydata.org/pandas-docs/stable/whatsnew/v0.25.0.html
that The .str-accessor performs stricter type checks. This was new since v.25
But I still dont know how to resolve this issue I am having with 'inferred bytes'


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

<details>

[paste the output of ``pd.show_versions()`` here below this line]

the working version

INSTALLED VERSIONS
------------------
commit: None
python: 3.6.7.final.0
python-bits: 64
OS: Linux
OS-release: 5.3.0-28-generic
machine: x86_64
processor: x86_64
byteorder: little
LC_ALL: None
LANG: en_US.UTF-8
LOCALE: en_US.UTF-8

pandas: 0.24.2
pytest: None
pip: 20.0.2
setuptools: 45.2.0.post20200209
Cython: None
numpy: 1.18.1
scipy: None
pyarrow: None
xarray: None
IPython: 7.12.0
sphinx: None
patsy: None
dateutil: 2.8.1
pytz: 2019.3
blosc: None
bottleneck: None
tables: None
numexpr: None
feather: None
matplotlib: 3.1.3
openpyxl: None
xlrd: None
xlwt: None
xlsxwriter: None
lxml.etree: None
bs4: None
html5lib: None
sqlalchemy: None
pymysql: None
psycopg2: None
jinja2: 2.11.1
s3fs: None
fastparquet: None
pandas_gbq: None
pandas_datareader: None
gcsfs: None


the crashing version

INSTALLED VERSIONS
------------------
commit           : None
python           : 3.7.6.final.0
python-bits      : 64
OS               : Linux
OS-release       : 5.3.0-28-generic
machine          : x86_64
processor        : x86_64
byteorder        : little
LC_ALL           : None
LANG             : en_US.UTF-8
LOCALE           : en_US.UTF-8

pandas           : 1.0.1
numpy            : 1.18.1
pytz             : 2019.3
dateutil         : 2.8.1
pip              : 20.0.2
setuptools       : 45.2.0.post20200209
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          : 7.12.0
pandas_datareader: None
bs4              : None
bottleneck       : None
fastparquet      : None
gcsfs            : None
lxml.etree       : None
matplotlib       : 3.1.3
numexpr          : None
odfpy            : None
openpyxl         : None
pandas_gbq       : None
pyarrow          : None
pytables         : None
pytest           : None
pyxlsb           : None
s3fs             : None
scipy            : 1.4.1
sqlalchemy       : None
tables           : None
tabulate         : None
xarray           : None
xlrd             : None
xlwt             : None
xlsxwriter       : None
numba            : None
</details>
