Issue with os.rename

[malinowy]

Hello experts,

I am facing this issue with os.rename

I have multiple scripts in my Jupyter notebook, and at some point I need to move some files to the "processed" folder.
When I run below code

import os
post_id='66ec21db97'
for s,n in majle.items():
    if n==post_id:
        d = re.sub(r'CCC\\',r'CCC\\processed\\',s)
        print('src - {}'.format(s))  
        print('dst - {}'.format(d))        
#         os.rename(s, d)

I am getting correct output:

src - C:\Users\marcin\Desktop\CCC\_External_ New Topic_ _Visio process map for customer account creation_ in Receivables & Collections.msg
dst - C:\Users\marcin\Desktop\CCC\processed\_External_ New Topic_ _Visio process map for customer account creation_ in Receivables & Collections.msg

But when I uncomment last line - os.rename(s, d), I am getting this error with double backslashes in my path:

Error:
PermissionError                           Traceback (most recent call last)
<ipython-input-11-b0460c8bfdbc> in <module>
      6         print('src - {}'.format(s))
      7         print('dst - {}'.format(d))
----> 8         os.rename(s, d)

PermissionError: [WinError 32] The process cannot access the file because it is being used by another process: 'C:\\Users\\marcin\\Desktop\\CCC\\_External_ New Topic_ _Visio process map for customer account creation_ in Receivables & Collections.msg' -> 'C:\\Users\\marcin\\Desktop\\CCC\\processed\\_External_ New Topic_ _Visio process map for customer account creation_ in Receivables & Collections.msg'

Is this the issue with backshales or some previous script indeed is blocking the file?
If so, how to release the the file?