Provide support for %dve and %require

* NEWS, python/spot/ltsmin.i,
tests/python/ltsmin.ipynb: Here.

NEWS

@@ -87,6 +87,9 @@ New in spot 1.99.7a (not yet released)
   * The ltsmin interface has been binded in Python.  See
     https://spot.lrde.epita.fr/ipynb/ltsmin.html for a short example.
 
+  * The ltsmin interface support two extra 'magic commands' when ipython
+    is used: %dve and %%require.
+
   * spot.setup() sets de maximum number of states to display in
     automata to 50 by default, as more states is likely to be
     unreadable (and slow to process by GraphViz).  This can be

python/spot/ltsmin.i

@@ -106,4 +106,80 @@ class model:
         res += type
       res += '\n';
     return res
+
+# Load IPython specific support if we can.
+try:
+    # Load only if we are running IPython.
+    __IPYTHON__
+
+    from IPython.core.magic import (Magics, magics_class, line_cell_magic)
+    from IPython.core.magic_arguments \
+        import (argument, magic_arguments, parse_argstring)
+    import os
+    import tempfile
+    import sys
+    import shutil
+    try:
+        import ipywidgets as widgets
+    except ImportError:
+        pass
+
+    # This class provides support for %%dve model description
+    @magics_class
+    class EditDVE(Magics):
+
+        @line_cell_magic
+        def dve(self, line, cell=None):
+            try:
+                # DiViNe prefers when files are in the current directory
+                # so write cell into local file
+                t = tempfile.NamedTemporaryFile(dir=os.getcwd())
+                filename = t.name + '.dve'
+                f = open(filename,"w")
+                f.write(cell)
+                f.close()
+
+                # Then compile and unlink temporary files
+                import subprocess
+                out=""
+                self.shell.user_ns[line] = None
+                out = subprocess.check_call(['divine', 'compile',
+                                       '--ltsmin', filename])
+                os.unlink(filename)
+                os.unlink(filename + '.cpp')
+                self.shell.user_ns[line] = load(filename + '2C')
+                os.unlink(filename + '2C')
+            except Exception as error:
+                try:
+                    os.unlink(filename)
+                    os.unlink(filename + '.cpp')
+                finally:
+                    if out != "":
+                        raise RuntimeError(out) from error
+                    raise error
+
+        @line_cell_magic
+        def require(self, line, cell=None):
+            if line != "divine":
+                print ("Unknown" + line, file=sys.stderr)
+                sys.exit(77)
+            if cell != None:
+                print ("No support for Cell magic command")
+                sys.exit(77)
+            if shutil.which("divine") == None:
+                print ("divine not available", file=sys.stderr)
+                sys.exit(77)
+            import subprocess
+            out = subprocess.check_output(['divine', 'compile',
+                                           '--help'], stderr=subprocess.STDOUT)
+            if b'LTSmin' not in out:
+                print ("divine available but no support for LTSmin",
+		       file=sys.stderr)
+                sys.exit(77)
+
+    ip = get_ipython()
+    ip.register_magics(EditDVE)
+
+except (ImportError, NameError):
+    pass
 %}