Your python3 install is corrupted. Please fix the '/usr/bin/python3' symlink.

i had the same problem with my python3 installation because i installed an alternative version. the default that came with ubuntu 18.04 was python3.6 and i had installed 3.7 & 3.8 and when ever i wanted to switch to the specific version i would use use update-alternative command. the issue with process is that it alters the default python3 simlink to point to the alternative installation path from

/usr/bin/python3.6

to

/etc/alternatives/python3

and the system expects that the first not the second even the terminal wouldn’t work so to restore to the default,

• remove alternative python installation (optional) but pointless to keep one when ubuntu 20.04 uses later version of python3

sudo update-alternative --remove python3 {/path/to/python3.7}

• restore the old (defulat) symlink of python3

sudo rm -rf /usr/bin/python3 && sudo ln -s /usr/bin/python3.6 /usr/bin/python3

and after that if you check your python3 symlink path

ls -la /usr/bin/python3.6

and it should point to the old (default) /usr/bin/python3.6

good luck and hope this helps.

Any update? I have manually install python2.7 and python3.7 after deleting the executable accidentally.

linux@linux:/usr/bin$ 
==> which python
/usr/bin/python
linux@linux:/usr/bin$ 
==> l python
lrwxrwxrwx 1 root root 24 May 22 00:47 python -> /usr/local/bin/python2.7
linux@linux:/usr/bin$ 
==> l python*
lrwxrwxrwx 1 root root 24 May 22 00:47 python -> /usr/local/bin/python2.7
lrwxrwxrwx 1 root root 22 May 22 00:47 python3 -> /usr/local/bin/python3
linux@linux:/usr/bin$ 
==> python --version
Python 3.7.4
linux@linux:/usr/bin$ 
==> lsb_release -a
Traceback (most recent call last):
  File "/usr/bin/lsb_release", line 25, in <module>
    import lsb_release
ModuleNotFoundError: No module named 'lsb_release'
linux@linux:/usr/bin$ 
==> sudo do-release-upgrade
Traceback (most recent call last):
  File "/usr/bin/do-release-upgrade", line 8, in <module>
    from DistUpgrade.DistUpgradeVersion import VERSION
ModuleNotFoundError: No module named 'DistUpgrade'

Seems i have done something to python. Now when i try sudo apt upgrade ,

i get

Processing was halted because there were too many errors.
E: Sub-process /usr/bin/dpkg returned an error code (1)```