message: Update sovrin_open_pool_ledger integration test.
diff: @@ -12,6 +12,8 @@ use sovrin::api::pool::{sovrin_create_pool_ledger_config, sovrin_open_pool_ledge
  mod environment;
  use environment::EnvironmentUtils;
  +use std::fs;
  +
  use std::ptr::null;
  use utils::callbacks::CallbacksHelpers;
  @@ -61,10 +63,16 @@ fn sovrin_open_pool_ledger_can_be_called() {
  let (command_handle, callback) = CallbacksHelpers::closure_to_open_pool_ledger_cb(cb);
  - let pool_name = CString::new("test1").unwrap();
  + let pool_name: String = "test1".to_string();
  + let c_pool_name = CString::new(pool_name.as_str()).unwrap();
  + let mut path = environment::EnvironmentUtils::pool_path(pool_name.as_str());
  + fs::create_dir_all(path.as_path()).unwrap();
  + path.push(pool_name);
  + path.set_extension("txn");
  + fs::File::create(path.as_path()).unwrap();
  let err = sovrin_open_pool_ledger(command_handle,
  - pool_name.as_ptr(),
  + c_pool_name.as_ptr(),
  null(),
  callback);
  @@ -74,9 +82,8 @@ fn sovrin_open_pool_ledger_can_be_called() {
  //TODO separate test to check error after open the same pool multiply times
  let (command_handle, callback) = CallbacksHelpers::closure_to_open_pool_ledger_cb(cb2);
  - let pool_name = CString::new("test1").unwrap();
  let err = sovrin_open_pool_ledger(command_handle,
  - pool_name.as_ptr(),
  + c_pool_name.as_ptr(),
  null(),
  callback);
  