in src/main/java/feign/error/ExceptionGenerator.java [177:185]
private void validateGeneratorCanBeUsedToGenerateExceptions(ExceptionGenerator generator) {
try {
generator.createException(TEST_RESPONSE);
} catch (Exception e) {
throw new IllegalStateException(
"Cannot generate exception - check constructor parameter types (are headers Map<String,Collection<String>> or is something causing an exception on construction?)",
e);
}
}