Define Beaker pool HW requirement

Related to #2346

spec/hardware/beaker.fmf

@@ -0,0 +1,21 @@
+summary: |
+    Select or provision a guest with Beaker-specific parameters.
+
+    .. note::
+
+        The requirements are consumed by Beaker-aware ``provision``
+        plugins only, and cannot be enforced in any other
+        infrastructure.
+
+description: |
+    .. code-block::
+
+       beaker:
+           # String, name of the Beaker pool to use for provisioning.
+           pool: "some-pool"
+
+example:
+  - |
+    # Select any system, as long as it is not from the given Beaker pool
+    beaker:
+        pool: "!= very-rare-machines"

tests/unit/provision/mrack/test_hw.py

@@ -50,6 +50,7 @@ def test_maximal_constraint(root_logger: Logger) -> None:
 
     assert result.to_mrack() == {
         'and': [
+            {'or': []},
             {'or': []},
             {
                 'and': [

tests/unit/test_hardware.py

@@ -145,6 +145,8 @@ def test_normalize_invalid_hardware(
 
 
 FULL_HARDWARE_REQUIREMENTS = """
+    beaker:
+        pool: "!= foo.*"
     boot:
         method: bios
     compatible:
@@ -219,6 +221,7 @@ def test_normalize_invalid_hardware(
 def test_parse_maximal_constraint() -> None:
     hw_spec_out = """
         and:
+          - beaker.pool: '!= foo.*'
           - boot.method: contains bios
           - and:
               - compatible.distro: contains rhel-7

tmt/hardware.py

@@ -1340,6 +1340,22 @@ def _parse_location(spec: Spec) -> BaseConstraint:
     return group
 
 
+@ungroupify
+def _parse_beaker(spec: Spec) -> BaseConstraint:
+    """
+    Parse constraints related to the ``beaker`` HW requirement.
+
+    :param spec: raw constraint block specification.
+    :returns: block representation as :py:class:`BaseConstraint` or one of its subclasses.
+    """
+
+    group = And()
+
+    group.constraints += _parse_text_constraints(spec, 'beaker', ('pool',))
+
+    return group
+
+
 @ungroupify
 def _parse_generic_spec(spec: Spec) -> BaseConstraint:
     """
@@ -1358,6 +1374,9 @@ def _parse_generic_spec(spec: Spec) -> BaseConstraint:
                 spec['arch'])
             ]
 
+    if 'beaker' in spec:
+        group.constraints += [_parse_beaker(spec['beaker'])]
+
     if 'boot' in spec:
         group.constraints += [_parse_boot(spec['boot'])]