Get rid from distutils module dependency (#1146)

We are using only one function from there, `find_executable()` and it is better to implement a similar function in Patroni rather than add `distutils` module into requirements.txt

patroni/ctl.py

@@ -25,7 +25,6 @@ import yaml
 
 from click import ClickException
 from contextlib import contextmanager
-from distutils.spawn import find_executable
 from patroni.config import Config
 from patroni.dcs import get_dcs as _get_dcs
 from patroni.exceptions import PatroniException
@@ -1107,6 +1106,24 @@ def apply_yaml_file(data, filename):
     return format_config_for_editing(changed_data), changed_data
 
 
+def find_executable(executable, path=None):
+    _, ext = os.path.splitext(executable)
+
+    if (sys.platform == 'win32') and (ext != '.exe'):
+        executable = executable + '.exe'
+
+    if os.path.isfile(executable):
+        return executable
+
+    if path is None:
+        path = os.environ.get('PATH', os.defpath)
+
+    for p in path.split(os.pathsep):
+        f = os.path.join(p, executable)
+        if os.path.isfile(f):
+            return f
+
+
 def invoke_editor(before_editing, cluster_name):
     """Starts editor command to edit configuration in human readable format
 

tests/test_ctl.py

@@ -9,7 +9,7 @@ from datetime import datetime, timedelta
 from mock import patch, Mock
 from patroni.ctl import ctl, store_config, load_config, output_members, request_patroni, get_dcs, parse_dcs, \
     get_all_members, get_any_member, get_cursor, query_member, configure, PatroniCtlException, apply_config_changes, \
-    format_config_for_editing, show_diff, invoke_editor, format_pg_version
+    format_config_for_editing, show_diff, invoke_editor, format_pg_version, find_executable
 from patroni.dcs.etcd import Client, Failover
 from patroni.utils import tzutc
 from psycopg2 import OperationalError
@@ -587,3 +587,12 @@ class TestCtl(unittest.TestCase):
     def test_format_pg_version(self):
         self.assertEqual(format_pg_version(100001), '10.1')
         self.assertEqual(format_pg_version(90605), '9.6.5')
+
+    @patch('sys.platform', 'win32')
+    def test_find_executable(self):
+        with patch('os.path.isfile', Mock(return_value=True)):
+            self.assertEqual(find_executable('vim'), 'vim.exe')
+        with patch('os.path.isfile', Mock(return_value=False)):
+            self.assertIsNone(find_executable('vim'))
+        with patch('os.path.isfile', Mock(side_effect=[False, True])):
+            self.assertEqual(find_executable('vim', '/'), '/vim.exe')