@Override
  public void visitBytecodeExpression(BytecodeExpression expr) {
    unsupported(); // cannot occur in condition
  }
Rewrites explicit ("assert x > 3") and implicit ("x > 3") condition
statements. Replacing the original statement with the rewritten one is up
to clients.

@author Peter Niederwieser
spock-core/src/main/java/org/spockframework/compiler/ConditionRewriter.java