mathter/1.0.0: WARN: This conanfile has no build step
ERROR: mathter/1.0.0: Error in package() method, line 44
	self.copy("*.hpp", dst=os.path.join("include", "Mathter"), src=os.path.join(_source_subfolder, "Mathter"))
	NameError: name '_source_subfolder' is not defined