Hashes are missing for some packages

[frostming]

• I have searched the issue tracker and believe that this is not a duplicate.

Make sure you run commands with -v flag before pasting the output.

Steps to reproduce

$ pdm init
$ pdm add numpy

Actual behavior

No hash for numpy

Expected behavior

Environment Information

pdm version:

# Paste the output of `pdm info && pdm info --env` below:
Python Interpreter: /Users/fming/Library/PythonUp/cmd/python3.7 (3.7.5)
Project Root:       /Users/fming/wkspace/github/pdm-test
{
  "implementation_name": "cpython",
  "implementation_version": "3.7.5",
  "os_name": "posix",
  "platform_machine": "x86_64",
  "platform_release": "19.3.0",
  "platform_system": "Darwin",
  "platform_version": "Darwin Kernel Version 19.3.0: Thu Jan  9 20:58:23 PST 2020; root:xnu-6153.81.5~1/RELEASE_X86_64",
  "python_full_version": "3.7.5",
  "platform_python_implementaiton": "CPython",
  "python_version": "3.7",
  "sys_platform": "darwin"
}