Add E722 bare-except documentation (#2796)

docs/rules/bare-except.md

@@ -0,0 +1,33 @@
+# bare-except (E722)
+
+Derived from the **pycodestyle** linter.
+
+## What it does
+Checks for bare `except` catches in `try`-`except` statements.
+
+## Why is this bad?
+A bare `except` catches `BaseException` which includes
+`KeyboardInterrupt`, `SystemExit`, `Exception`, and others. Catching
+`BaseException` can make it hard to interrupt the program (e.g., with
+Ctrl-C) and disguise other problems.
+
+## Example
+```python
+try:
+    raise(KeyboardInterrupt("You probably don't mean to break CTRL-C."))
+except:
+    print("But a bare `except` will ignore keyboard interrupts.")
+```
+
+Use instead:
+```python
+try:
+    do_something_that_might_break()
+except MoreSpecificException as e:
+    handle_error(e)
+```
+
+## References
+- [PEP 8](https://www.python.org/dev/peps/pep-0008/#programming-recommendations)
+- [Python: "Exception hierarchy"](https://docs.python.org/3/library/exceptions.html#exception-hierarchy)
+- [Google Python Style Guide: "Exceptions"](https://google.github.io/styleguide/pyguide.html#24-exceptions)