test: Library checking script for tests

Storage role development often relies on blivet library and changes in
it. Whether or not is specific feature supported by blivet is usually determined
by its version. That is a cumbersome process, especially when the feature
has not yet been added into blivet and the version has to be guessed.

Added script verifies existence of the feature by using python
introspection and asking for existence of specific item in the library
(e.g. 'blivet.formats.lvmpv.LVMPhysicalVolume.grow_to_fill').
The script is supposed to be used for the tests only.

tests/scripts/does_library_support.py

@@ -0,0 +1,55 @@
+#!/usr/bin/python
+
+# This script checks for blivet compatibility by trying to access
+# blivet parts specified by given parameter
+# Returns True if part is found, False otherwise
+
+# The script is meant to be a supporting tool for the storage role tests
+import sys
+import blivet
+import importlib
+
+def is_supported(var):
+
+    parts = var.split('.')
+    imports = ''
+    obj = sys.modules[__name__]
+
+    # try to import each part
+    while parts:
+        part = parts.pop(0)
+        imports += part + '.'
+
+        try:
+            importlib.import_module(imports.rstrip('.'))
+        except ImportError:
+            break
+
+        # generate access to the object for later use
+        obj = getattr(obj, part)
+
+    else:
+        # break did not happen in the cycle 
+        # it means the whole string was importable
+        return True
+
+    # part of the string was not importable, the rest can be attributes
+
+    # get part back to parts to simplify the following loop
+    parts = [part] + parts
+
+    while parts:
+        part = parts.pop(0)
+        obj = getattr(obj, part, None)
+
+        if obj is None:
+            return False
+
+    return True
+
+if __name__ == "__main__":
+    if len(sys.argv) != 2:
+        print("Usage: python %s <parameter>" % sys.argv[0])
+        sys.exit(-1)
+
+    print(is_supported(sys.argv[1]))