[cleanup][Python] Remove portalocker dependency.

dune.module

@@ -4,5 +4,5 @@ Author: The Dune Core developers
 Maintainer: dune-devel@lists.dune-project.org
 Description: Basis infrastructure for all Dune modules
 URL: https://gitlab.dune-project.org/core/dune-common
-Python-Requires: pip>=21 portalocker numpy wheel jinja2 mpi4py
+Python-Requires: pip>=21 numpy wheel jinja2 mpi4py
 Whitespace-Hook: Yes

pyproject.toml

@@ -10,5 +10,5 @@
 # included in the package install from source.
 #
 [build-system]
-requires = ['cmake', 'jinja2', 'mpi4py', 'ninja', 'numpy', 'pip>=21.0.0', 'portalocker', 'requests', 'scikit-build', 'setuptools', 'wheel']
+requires = ['cmake', 'jinja2', 'mpi4py', 'ninja', 'numpy', 'pip>=21.0.0', 'requests', 'scikit-build', 'setuptools', 'wheel']
 build-backend = 'setuptools.build_meta'

python/dune/common/locking.py

-## By default use portalocker, if available.
-## However, portalocker is not available on all systems
-## and therefore a fallback implementation is also provided
-try:
-    from portalocker import Lock as _Lock
-    from portalocker.constants import LOCK_EX, LOCK_SH
-    class Lock(_Lock):
-        def __init__(self, path, flags, *args, **kwargs):
-            _Lock.__init__(self,path,*args,flags=flags,timeout=None,**kwargs)
-except ModuleNotFoundError:
-    ## Fallback implementation if portalocker was not found
-    ## This is still needed! Do not remove it.
-    import os
-    import fcntl
-    from fcntl import LOCK_EX, LOCK_SH
-    # file locking from fcntl
-    def lock_file(f, cmd=fcntl.LOCK_EX):
-        fcntl.flock(f, cmd)
-        return f
-    def unlock_file(f):
-        fcntl.flock(f, fcntl.LOCK_UN)
-        return f
+import os
+import fcntl
+from fcntl import LOCK_EX, LOCK_SH
+# file locking from fcntl
+def lock_file(f, cmd=fcntl.LOCK_EX):
+    fcntl.flock(f, cmd)
+    return f
+def unlock_file(f):
+    fcntl.flock(f, fcntl.LOCK_UN)
+    return f
 
-    # This file opener *must* be used in a "with" block.
-    class Lock:
-        # Open the file with arguments provided by user. Then acquire
-        # a lock on that file object (WARNING: Advisory locking).
-        def __init__(self, path, flags, *args, **kwargs):
-            # Open the file and acquire a lock on the file before operating
-            self.file = open(path, mode='w+', *args, **kwargs)
-            # Lock the opened file
-            self.file = lock_file(self.file, flags) # flags are either LOCK_EX or LOCK_SH
+# This file opener *must* be used in a "with" block.
+class Lock:
+    # Open the file with arguments provided by user. Then acquire
+    # a lock on that file object (WARNING: Advisory locking).
+    def __init__(self, path, flags, *args, **kwargs):
+        # Open the file and acquire a lock on the file before operating
+        self.file = open(path, mode='w+', *args, **kwargs)
+        # Lock the opened file
+        self.file = lock_file(self.file, flags) # flags are either LOCK_EX or LOCK_SH
 
-        # Return the opened file object (knowing a lock has been obtained).
-        def __enter__(self, *args, **kwargs): return self.file
+    # Return the opened file object (knowing a lock has been obtained).
+    def __enter__(self, *args, **kwargs): return self.file
 
-        # Unlock the file and close the file object.
-        def __exit__(self, exc_type=None, exc_value=None, traceback=None):
-            # Flush to make sure all buffered contents are written to file.
-            self.file.flush()
-            os.fsync(self.file.fileno())
-            # Release the lock on the file.
-            self.file = unlock_file(self.file)
-            self.file.close()
-            # Handle exceptions that may have come up during execution, by
-            # default any exceptions are raised to the user.
-            return exc_type == None
+    # Unlock the file and close the file object.
+    def __exit__(self, exc_type=None, exc_value=None, traceback=None):
+        # Flush to make sure all buffered contents are written to file.
+        self.file.flush()
+        os.fsync(self.file.fileno())
+        # Release the lock on the file.
+        self.file = unlock_file(self.file)
+        self.file.close()
+        # Handle exceptions that may have come up during execution, by
+        # default any exceptions are raised to the user.
+        return exc_type == None