Internal error multiline docstring with tab

[adampinky85]

Describe the bug
Internal error is thrown parsing a multi-line docstring which includes a tab. This issue appears to be a regression upgrading between black 19.10b0 and 20.8b1.

To Reproduce

def tab_internal_error():
    """
    Param:	<- tab before description fails to parse
    """
    pass

INTERNAL ERROR: Black produced code that is not equivalent to the source.

--- src
+++ dst
@@ -16,11 +16,11 @@
       body=
         Expr(
           value=
             Constant(
               value=
-                'Param:\t<- tab before description fails to parse',  # str
+                'Param:      <- tab before description fails to parse',  # str
             )  # /Constant
         )  # /Expr
         Pass(
         )  # /Pass
       decorator_list=

Expected behavior
n/a

Environment
Ubuntu 20.04.1 LTS
Python 3.8.6
black==20.8b1

Does this bug also happen on master?
Yes reproducible from the minimal viable example on the master black playground

Additional context
Thanks to all involved in the project. Black has materially improved the quality of our code and is a core part of our CI/CD.

[ichard26]

Closing as this has been fixed by #1128:

(black) ichard26@acer-ubuntu:~/programming/oss/black$ python --version
Python 3.8.5
(black) ichard26@acer-ubuntu:~/programming/oss/black$ lsb_release -a
No LSB modules are available.
Distributor ID:	Ubuntu
Description:	Ubuntu 20.04.1 LTS
Release:	20.04
Codename:	focal
(black) ichard26@acer-ubuntu:~/programming/oss/black$ git log -n 1 --oneline
1d8b4d7 (HEAD -> main, upstream/master) Correctly handle inline tabs in docstrings (#1810)
(black) ichard26@acer-ubuntu:~/programming/oss/black$ black test.py --diff --color
All done! ✨ 🍰 ✨
1 file would be left unchanged.