[config] Improve Parse Error
[config] Improve Parse Error

Use a specific error type for parsing errors.

Closes: #1865
Approved by: bmwill

libra/libra,aptos-labs/aptos-core,libra/libra,libra/libra,aptos-labs/aptos-core,aptos-labs/aptos-core,libra/libra,aptos-labs/aptos-core,aptos-labs/aptos-core,libra/libra,aptos-labs/aptos-core,aptos-labs/aptos-core