Use pathlib in `sys.path` manipulation examples

doc/development/tutorials/extending_build.rst

@@ -313,10 +313,10 @@ For example:
 
 .. code-block:: python
 
-   import os
    import sys
+   from pathlib import Path
 
-   sys.path.append(os.path.abspath("./_ext"))
+   sys.path.append(str(Path('_ext').resolve()))
 
    extensions = ['todo']
 

doc/development/tutorials/extending_syntax.rst

@@ -169,10 +169,10 @@ For example:
 
 .. code-block:: python
 
-   import os
    import sys
+   from pathlib import Path
 
-   sys.path.append(os.path.abspath("./_ext"))
+   sys.path.append(str(Path('_ext').resolve()))
 
    extensions = ['helloworld']