Problem/Motivation
See #2735005: Convert all Simpletest web tests to BrowserTestBase (or UnitTestBase/KernelTestBase).
This will also involve converting cURL calls to Guzzle because cURL is not compatible with BTB.
\Drupal\history\tests\HistoryTest has a couple of curlExec calls, which are:
a) hard to read
b) not compatible with BTB
Proposed resolution
Move it to use guzzle directly.