Log more accurate error when $ act purchase fails

[vipyne]

Expected Behavior

$ act purchase <purchaser> <did>
...
ara: error: fatal: ongoing transaction; failed to submit the new transaction

Actual Behavior

$ act purchase <purchaser> <did>
...
ara: error: fatal: replacement transaction underpriced

Steps to Reproduce the Problem

1. Make two purchases at the same time via CLI

Specifications

• Version: 0.11.3
• Platform:
• Subsystem:

[mahjiang]

Unfortunately Web3 doesn't give us helpful errors when things like this happen, but we will keep an eye out for Web3 improvements and make updates as they come!