old_contents: from conans import ConanFile, CMake
  
  class CausalSetsExplorer(ConanFile):
      settings = "os", "compiler", "build_type", "arch"
      requires = "boost/1.67.0@conan/stable", "catch2/2.3.0@bincrafters/stable"
      generators = "cmake"
      default_options = "Boost:header_only=True"
  
      def build(self):
          cmake = CMake(self)
          cmake.verbose = True
          cmake.configure(args=["CMAKE_BUILD_TYPE=Release"])
          cmake.build()
  
      def build_requirements(self):
          # AppVeyor already has modern CMake installed
          if self.settings.os != "Windows":
              self.build_requires("cmake_installer/3.11.3@conan/stable")
new_contents: from conans import ConanFile, CMake
  
  class CausalSetsExplorer(ConanFile):
      settings = "os", "compiler", "build_type", "arch"
      requires = "boost/1.67.0@conan/stable", "catch2/2.2.2@bincrafters/stable"
      generators = "cmake"
      default_options = "Boost:header_only=True"
  
      def build(self):
          cmake = CMake(self)
          cmake.verbose = True
          cmake.configure(args=["CMAKE_BUILD_TYPE=Release"])
          cmake.build()
  
      def build_requirements(self):
          # AppVeyor already has modern CMake installed
          if self.settings.os != "Windows":
              self.build_requires("cmake_installer/3.11.3@conan/stable")
subject: Revert back to older Catch2, part 2