Remove exit error types

[kmoe]

Closes #296.

This PR proposes a breaking change to the terraform-exec API removing the following error types:
ErrConfigInvalid
ErrLockIdInvalid
ErrMissingVar
ErrNoConfig
ErrNoInit
ErrNoWorkspace
ErrStateLocked
ErrStatePlanRead
ErrTFVersionMismatch
ErrWorkspaceExists

The above error types are returned based on parsing the human-readable output of Terraform CLI via regex. The human-readable output of Terraform CLI is not designed for machine parsing, and can change at any time, as it is not covered by the Terraform v1.x Compatibility Promises. These changes, along with trivial text formatting issues, are a common cause of test failures in terraform-exec.

I don't think maintaining these is worth the work, in the absence of a clear use case for these errors. If you have one, please comment here or on the linked issue.

Note that the following errors are not removed:
ErrVersionMismatch
ErrNoSuitableBinary
ErrManualEnvVar

In particular, the compatibility error ErrVersionMismatch, which is based on terraform-exec's knowledge of which flags and commands can be used with which version of Terraform, is not removed.

---

As Terraform's machine-readable UI (-json streaming format) matures, I expect Terraform itself is the best place to build more structure into errors and diagnostics if necessary. For example, diagnostics could contain an error symbol in addition to their human-readable summary and description.

[bflad]

Looks good to me 🚀

[bflad]

Nit: Not sure if its worth checking for the (new) expected error in these cases or not.

[radeksimko]

The proposed change in principle LGTM, but there's now a number of tests which are failing, so I think we either need to reconsider the scope, or change the tests.

[kmoe]

Rebased, but this change unintentionally broke the context.DeadlineExceeded wrapping introduced in 592bcd1 (see golang/go#21880). Fixing.

[radeksimko]

I didn't do any "deeper" checks in terms of reading through the relevant LS code, but I can confirm that all LS tests are still passing with these changes, i.e. we aren't relying on any of the error types being removed in LS.

Let's ship it!

Time will tell how much we're affected by Hyrum's Law 😁

[sergiught]

This change unfortunately makes all our test cases that expect an error fail within https://github.com/auth0/terraform-provider-auth0 e.g.

func TestAccBranding_WithNoCustomDomainsSet(t *testing.T) {
	acctest.Test(t, resource.TestCase{
		Steps: []resource.TestStep{
			{
				Config: testAccTenantDisallowsUniversalLoginCustomization,
				ExpectError: regexp.MustCompile(
					"managing the universal login body through the 'auth0_branding' resource " +
						"requires at least one custom domain to be configured for the tenant",
				),
			},
		},
	})
}

To reproduce:

git clone git@github.com:auth0/terraform-provider-auth0.git
cd terraform-provider-auth0
go mod vendor
make test-acc FILTER="TestAccBranding_WithNoCustomDomainsSet" // test passing
go get github.com/hashicorp/terraform-exec@v0.18.0
go mod vendor
make test-acc FILTER="TestAccBranding_WithNoCustomDomainsSet" // test failing

[kmoe]

Thanks @sergiught, we're looking into this now. Stderr did not make it into the error wrapping, it seems.