Switch to keybase go-crypto (for some elliptic curve key) + test (#1925)

* Switch to keybase go-crypto (for some elliptic curve key) + test

* Use assert.NoError 

and add a little more context to failing test description

* Use assert.(No)Error everywhere 🌈

and assert.Error in place of .Nil/.NotNil

vendor/github.com/keybase/go-crypto/openpgp/errors/errors.go

@@ -0,0 +1,72 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package errors contains common error types for the OpenPGP packages.
+package errors // import "github.com/keybase/go-crypto/openpgp/errors"
+
+import (
+	"strconv"
+)
+
+// A StructuralError is returned when OpenPGP data is found to be syntactically
+// invalid.
+type StructuralError string
+
+func (s StructuralError) Error() string {
+	return "openpgp: invalid data: " + string(s)
+}
+
+// UnsupportedError indicates that, although the OpenPGP data is valid, it
+// makes use of currently unimplemented features.
+type UnsupportedError string
+
+func (s UnsupportedError) Error() string {
+	return "openpgp: unsupported feature: " + string(s)
+}
+
+// InvalidArgumentError indicates that the caller is in error and passed an
+// incorrect value.
+type InvalidArgumentError string
+
+func (i InvalidArgumentError) Error() string {
+	return "openpgp: invalid argument: " + string(i)
+}
+
+// SignatureError indicates that a syntactically valid signature failed to
+// validate.
+type SignatureError string
+
+func (b SignatureError) Error() string {
+	return "openpgp: invalid signature: " + string(b)
+}
+
+type keyIncorrectError int
+
+func (ki keyIncorrectError) Error() string {
+	return "openpgp: incorrect key"
+}
+
+var ErrKeyIncorrect error = keyIncorrectError(0)
+
+type unknownIssuerError int
+
+func (unknownIssuerError) Error() string {
+	return "openpgp: signature made by unknown entity"
+}
+
+var ErrUnknownIssuer error = unknownIssuerError(0)
+
+type keyRevokedError int
+
+func (keyRevokedError) Error() string {
+	return "openpgp: signature made by revoked key"
+}
+
+var ErrKeyRevoked error = keyRevokedError(0)
+
+type UnknownPacketTypeError uint8
+
+func (upte UnknownPacketTypeError) Error() string {
+	return "openpgp: unknown packet type: " + strconv.Itoa(int(upte))
+}