Unable to install missing types

[tpazderka]

Bug Report

Mypy segfaults on installation of missing types.

To Reproduce

1. mypy project
2. mypy --install-types

Expected Behavior

Mypy would install the missing library stubs.

Actual Behavior

Mypy reports segmentation fault with no traceback (even with --tb on).
Your Environment

• Mypy version used: 0.900
• Mypy command-line flags: none
• Mypy configuration options from mypy.ini (and other config files):

check_untyped_defs = true                                                                                                                                                                                                                                 
ignore_missing_imports = true   

• Python version used: 3.8.6 (pyenv, tox), 3.9.0 (system)
• Operating system and version: Debian

[JukkaL]

Closing as duplicate of #10596.