src/sage/features/mwrank.py: new feature for the mwrank program

The meson build system is now capable of building sagelib without
linking to libec, which means that the mwrank program may not be
installed. Here we add a new feature to represent it. In particular
this allows us to use "needs mwrank" in tests.

Author: orlitzky

src/sage/features/mwrank.py

@@ -0,0 +1,34 @@
+# sage_setup: distribution = sagemath-environment
+r"""
+Feature for testing the presence of the ``mwrank`` program (part
+of eclib)
+"""
+
+from . import Executable, FeatureTestResult
+
+
+class Mwrank(Executable):
+    r"""
+    A :class:`~sage.features.Feature` describing the presence of
+    the ``mwrank`` program.
+
+    EXAMPLES::
+
+        sage: from sage.features.mwrank import Mwrank
+        sage: Mwrank().is_present()  # needs mwrank
+        FeatureTestResult('mwrank', True)
+    """
+    def __init__(self):
+        r"""
+        TESTS::
+
+            sage: from sage.features.mwrank import Mwrank
+            sage: isinstance(Mwrank(), Mwrank)
+            True
+        """
+        Executable.__init__(self, 'mwrank', executable='mwrank',
+                            spkg='eclib', type='standard')
+
+
+def all_features():
+    return [Mwrank()]