Address more @asottile's review comments

pre_commit/languages/python.py

@@ -68,6 +68,8 @@ def _find_by_sys_executable():
 def _get_default_version():  # pragma: no cover (platform dependent)
     # First attempt from `sys.executable` (or the realpath)
     exe = _find_by_sys_executable()
+    if exe:
+        return exe
 
     # Next try the `pythonX.X` executable
     exe = 'python{}.{}'.format(*sys.version_info)

tests/languages/python_test.py

@@ -7,7 +7,7 @@ import sys
 import mock
 import pytest
 
-import pre_commit.parse_shebang
+from pre_commit import parse_shebang
 from pre_commit.languages import python
 
 
@@ -50,7 +50,7 @@ def test_find_by_sys_executable(exe, realpath, expected):
     with mock.patch.object(sys, 'executable', exe):
         with mock.patch.object(os.path, 'realpath', return_value=realpath):
             with mock.patch.object(
-                pre_commit.parse_shebang, 'find_executable',
+                parse_shebang, 'find_executable',
                 side_effect=mocked_find_executable,
             ):
                 assert python._find_by_sys_executable() == expected