Looks like cannot download the mapping

[Tnze]

Tnze:DecompilerMC Tnze$ python3 main.py 
Please Run once the snapshot/version on your computer via Minecraft Launcher so it can download it
Please input you decompiler choice: fernflower (f) or cfr (default: cfr) : 
Please input a valid version starting from 19w36a and 1.14.4 : 19w36a
/src/19w36a already exists, wipe it (w), create a new folder (n) or kill the process (k) ? w
Download mappings? (y/n): y
Found 19w36a.json
Downloading the mappings for 19w36a...
Downloading mappings/19w36a/client.txt...
URL Error
<urlopen error [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: unable to get local issuer certificate (_ssl.c:1051)>
Done!
Remap mappings to tsrg? (y/n): n
Remap? (y/n): y
=== Remapping jar using SpecialSource ====
ERROR: Missing files
Decompile? (y/n): y
=== Decompiling using CFR (silent) ===
ERROR: Missing files
===FINISHED===
Press Enter key to exit

[Neil]

this looks like a local ssl error due to your distribution, please accept mojang certificate or update your keys/ssl modules

[Tnze]

Or can I download it manually?

[Neil]

sure

[Neil]

https://launcher.mojang.com/v1/objects/a981dbf4095dbb2ffb078db14d676fb8f9c2fa99/client.txt for 19w36a

[Neil]

https://launcher.mojang.com/v1/objects/c0c8ef5131b7beef2317e6ad80ebcd68c4fb60fa/client.txt for 1.14.4

[Neil]

put it in the mappings folder