Fix flake8 warnings.

src/pricehist/outputs/beancount.py

@@ -10,9 +10,11 @@ the Beancount format in mind.
 
 Relevant sections of the Beancount documentation:
 
-* `Commodities / Currencies <https://beancount.github.io/docs/beancount_language_syntax.html#commodities-currencies>`_
+* `Commodities / Currencies
+   <https://beancount.github.io/docs/beancount_language_syntax.html#commodities-currencies>`_
 * `Prices <https://beancount.github.io/docs/beancount_language_syntax.html#prices>`_
-* `Fetching Prices in Beancount <https://beancount.github.io/docs/fetching_prices_in_beancount.html>`_
+* `Fetching Prices in Beancount
+   <https://beancount.github.io/docs/fetching_prices_in_beancount.html>`_
 
 Classes:
 

src/pricehist/outputs/ledger.py

@@ -11,8 +11,10 @@ format.
 
 Relevant sections of the Ledger manual:
 
-* `Commodities and Currencies <https://www.ledger-cli.org/3.0/doc/ledger3.html#Commodities-and-Currencies>`_
+* `Commodities and Currencies
-* `Commoditized Amounts <https://www.ledger-cli.org/3.0/doc/ledger3.html#Commoditized-Amounts>`_
+   <https://www.ledger-cli.org/3.0/doc/ledger3.html#Commodities-and-Currencies>`_
+* `Commoditized Amounts
+   <https://www.ledger-cli.org/3.0/doc/ledger3.html#Commoditized-Amounts>`_
 
 Relevant sections of the hledger manual:
 

src/pricehist/sources/basesource.py

@@ -1,5 +1,4 @@
 import logging
-import sys
 from abc import ABC, abstractmethod
 from textwrap import TextWrapper
 

tests/pricehist/test_exceptions.py

@@ -1,5 +1,4 @@
 import logging
-import sys
 
 import pytest