Improve log errors

With the current log error call log message sent to Sentry are being truncated.

https://github.com/graphql-python/graphql-core/blob/master/graphql/execution/utils.py#L155

https://forum.sentry.io/t/tracebacks-are-being-truncated/7304/2

One solution is to use `log.error()` with `exc_info=True`.

https://forum.sentry.io/t/some-stack-traces-are-truncated/7309

Start at graphql/execution/utils.py line 155 and review the linked Sentry discussions about truncated tracebacks. Confirm the logging change preserves the full error information in Sentry, then verify the relevant project checks pass.

Written by the indexing model from the issue text.