More cleaning and enforcing of types.

Also drop some reminder python 2 compatibility imports. And use some
context manager when appropriate instead of manual closing

IPython/paths.py

@@ -70,7 +70,7 b' def get_ipython_dir() -> str:'
     return ipdir
 
 
-def get_ipython_cache_dir():
+def get_ipython_cache_dir() -> str:
     """Get the cache directory it is created if it does not exist."""
     xdgdir = get_xdg_cache_dir()
     if xdgdir is None:
@@ -81,13 +81,14 b' def get_ipython_cache_dir():'
     elif not _writable_dir(xdgdir):
         return get_ipython_dir()
 
-    return py3compat.cast_unicode(ipdir, fs_encoding)
+    return ipdir
 
 
-def get_ipython_package_dir():
+def get_ipython_package_dir() -> str:
     """Get the base directory where IPython itself is installed."""
     ipdir = os.path.dirname(IPython.__file__)
-    return py3compat.cast_unicode(ipdir, fs_encoding)
+    assert isinstance(ipdir, str)
+    return ipdir
 
 
 def get_ipython_module_path(module_str):

IPython/utils/path.py

@@ -169,7 +169,7 b' class HomeDirError(Exception):'
     pass
 
 
-def get_home_dir(require_writable=False):
+def get_home_dir(require_writable=False) -> str:
     """Return the 'home' directory, as a unicode string.
 
     Uses os.path.expanduser('~'), and checks for writability.
@@ -197,21 +197,18 b' def get_home_dir(require_writable=False):'
     if not _writable_dir(homedir) and os.name == 'nt':
         # expanduser failed, use the registry to get the 'My Documents' folder.
         try:
-            try:
-                import winreg as wreg  # Py 3
-            except ImportError:
-                import _winreg as wreg  # Py 2
-            key = wreg.OpenKey(
+            import winreg as wreg
+            with wreg.OpenKey(
                 wreg.HKEY_CURRENT_USER,
                 r"Software\Microsoft\Windows\CurrentVersion\Explorer\Shell Folders"
-            )
-            homedir = wreg.QueryValueEx(key,'Personal')[0]
-            key.Close()
+            ) as key:
+                homedir = wreg.QueryValueEx(key,'Personal')[0]
         except:
             pass
 
     if (not require_writable) or _writable_dir(homedir):
-        return py3compat.cast_unicode(homedir, fs_encoding)
+        assert isinstance(homedir, str), "Homedir shoudl be unicode not bytes"
+        return homedir
     else:
         raise HomeDirError('%s is not a writable dir, '
                 'set $HOME environment variable to override' % homedir)