Don't assume grandparent process is the shell

- Windows only (pew implementation bug)
- Traverse process tree until we find a known shell
  like cmd or powershell currently

pipenv/patched/pew/_win_utils.py

@@ -105,3 +105,22 @@ def get_grandparent_process(pid=None):
     parent = processes[ppid]
     grandparent = processes[parent['parent_pid']]
     return grandparent['executable']
+
+
+def get_shell(pid=None):
+    """Get the shell that the supplied pid or os.getpid() is running in.
+    """
+    if not pid:
+        pid = os.getpid()
+    processes = get_all_processes()
+
+    def check_parent(pid, lvl=0):
+        ppid = processes[pid].get('parent_pid')
+        if ppid and processes[ppid]['executable'].lower().rsplit('.', 1)[0] in ['cmd', 'powershell']:
+            return processes[ppid]['executable']
+        if lvl >= 4:
+            return
+        return check_parent(ppid, lvl=lvl+1)
+    if processes[pid]['executable'].lower().rsplit('.', 1)[-1] in ['cmd', 'powershell']:
+        return processes[pid]['executable']
+    return check_parent(pid)

pipenv/patched/pew/pew.py

@@ -36,7 +36,7 @@ else:
     InstallCommand = ListPythons = LocatePython = UninstallCommand = \
         lambda : sys.exit('Command not supported on this platform')
 
-    from ._win_utils import get_grandparent_process
+    from ._win_utils import get_shell
 
 from pew._utils import (check_call, invoke, expandpath, own, env_bin_dir,
                         check_path, temp_environ, NamedTemporaryFile, to_unicode)
@@ -184,7 +184,7 @@ def _detect_shell():
         if 'CMDER_ROOT' in os.environ:
             shell = 'Cmder'
         elif windows:
-            shell = get_grandparent_process(os.getpid())
+            shell = get_shell(os.getpid())
         else:
             shell = 'sh'
     return shell
@@ -196,7 +196,7 @@ def shell(env, cwd=None):
     if shell_name not in ('Cmder', 'bash', 'elvish', 'powershell', 'klingon', 'cmd'):
         # On Windows the PATH is usually set with System Utility
         # so we won't worry about trying to check mistakes there
-        shell_check = (sys.executable + ' -c "from pew.pew import '
+        shell_check = (sys.executable + ' -c "from pipenv.patched.pew import '
                        'prevent_path_errors; prevent_path_errors()"')
         try:
             inve(env, shell, '-c', shell_check)