else-if checker throwing an IndexError

[niothiel]

Steps to reproduce

1. Create a file with the contents:

print(f'{"foo" if True else "N/A"}')
if "foo" == "bar":
    pass
elif "bar" == "baz":
    pass

2. Configure pylint to include the pylint.extensions.check_elif extension
3. Run pylint {file}.py

Current behavior

The elif checker throws an IndexError:

Traceback (most recent call last):
  File ".../bin/pylint", line 11, in <module>
    sys.exit(run_pylint())
  File ".../lib/python3.7/site-packages/pylint/__init__.py", line 20, in run_pylint
    Run(sys.argv[1:])
  File ".../lib/python3.7/site-packages/pylint/lint.py", line 1628, in __init__
    linter.check(args)
  File ".../lib/python3.7/site-packages/pylint/lint.py", line 943, in check
    self._do_check(files_or_modules)
  File ".../lib/python3.7/site-packages/pylint/lint.py", line 1075, in _do_check
    self.check_astroid_module(ast_node, walker, rawcheckers, tokencheckers)
  File ".../lib/python3.7/site-packages/pylint/lint.py", line 1158, in check_astroid_module
    walker.walk(ast_node)
  File ".../lib/python3.7/site-packages/pylint/utils.py", line 1303, in walk
    self.walk(child)
  File ".../lib/python3.7/site-packages/pylint/utils.py", line 1303, in walk
    self.walk(child)
  File ".../lib/python3.7/site-packages/pylint/utils.py", line 1300, in walk
    cb(astroid)
  File ".../lib/python3.7/site-packages/pylint/extensions/check_elif.py", line 63, in visit_if
    if not self._elifs[self._if_counter]:
IndexError: list index out of range

Expected behavior

The checker completes successfully.

pylint --version output

pylint 2.3.1
astroid 2.2.5
Python 3.7.1 (default, Dec 13 2018, 10:54:03) 
[Clang 10.0.0 (clang-1000.10.44.4)]

Basic Analysis

It looks like there is a conflict with elif and how the f-string is parsed for if statements. I've observed that either excluding the elif or removing the f-string, pylint completes successfully. I'm not sure if this is best reported here or against astroid or some other place entirely. Please feel free to move as appropriate. :)