atom: implement __str__() for Blocker and SlotOperator enums

Author: radhermit

src/pkgcraft/atom/base.pyx

@@ -1,5 +1,5 @@
 import functools
-from enum import Enum
+from enum import IntEnum
 
 cimport cython
 
@@ -196,7 +196,7 @@ def _cached_atom(cls, atom, eapi=None):
     return cls(atom, eapi)
 
 
-class Blocker(Enum):
+class Blocker(IntEnum):
     Strong = C.BLOCKER_STRONG
     Weak = C.BLOCKER_WEAK
 
@@ -207,8 +207,14 @@ class Blocker(Enum):
             return Blocker(blocker)
         raise ValueError(f'invalid blocker: {s}')
 
+    def __str__(self):
+        c_str = C.pkgcraft_atom_blocker_str(self)
+        s = c_str.decode()
+        C.pkgcraft_str_free(c_str)
+        return s
+
 
-class SlotOperator(Enum):
+class SlotOperator(IntEnum):
     Equal = C.SLOT_OPERATOR_EQUAL
     Star = C.SLOT_OPERATOR_STAR
 
@@ -219,6 +225,12 @@ class SlotOperator(Enum):
             return SlotOperator(slot_op)
         raise ValueError(f'invalid slot operator: {s}')
 
+    def __str__(self):
+        c_str = C.pkgcraft_atom_slot_op_str(self)
+        s = c_str.decode()
+        C.pkgcraft_str_free(c_str)
+        return s
+
 
 @cython.final
 cdef class Atom(Cpv):

src/pkgcraft/pkgcraft_c.pxd

@@ -149,6 +149,9 @@ cdef extern from "pkgcraft.h":
     # The argument should be a UTF-8 string.
     int pkgcraft_atom_blocker_from_str(const char *s)
 
+    # Return the string for a Blocker.
+    char *pkgcraft_atom_blocker_str(Blocker b)
+
     # Return an atom's category, e.g. the atom "=cat/pkg-1-r2" has a category of "cat".
     #
     # # Safety
@@ -260,6 +263,9 @@ cdef extern from "pkgcraft.h":
     # The argument should be a UTF-8 string.
     int pkgcraft_atom_slot_op_from_str(const char *s)
 
+    # Return the string for a SlotOperator.
+    char *pkgcraft_atom_slot_op_str(SlotOperator op)
+
     # Return the string for an atom.
     #
     # # Safety