providercache: Improve installation error message

[radeksimko]

Target Release

1.4.x

Draft CHANGELOG entry

ENHANCEMENTS

• providercache: show why a provider couldn't be installed (e.g. lack of permissions)

---

Context

On Windows, when Terraform doesn't have TMP or other environment variable which would hint where to create temporary files, the stdlib ioutil.TempDir() chooses C:\Windows. This directory in turn typically requires elevated privileges for writing which common user does not have.

See also hashicorp/terraform-exec#337

Before

Error: Failed to install provider

Error while installing hashicorp/local v2.2.3: failed to open temporary file
to download from
https://releases.hashicorp.com/terraform-provider-local/2.2.3/terraform-provider-local_2.2.3_windows_amd64.zip

After

Error: Failed to install provider

Error while installing hashicorp/local v2.2.3: failed to open temporary file
to download from
https://releases.hashicorp.com/terraform-provider-local/2.2.3/terraform-provider-local_2.2.3_windows_amd64.zip:
open C:\Windows\terraform-provider1818936128: Access is denied.

[kmoe]

Thank you!

[github-actions]

Reminder for the merging maintainer: if this is a user-visible change, please update the changelog on the appropriate release branch.

[github-actions]

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