Better error reporting on bad datashapes #387

ds2 = """ var * {
  currently: {
    apparentTemperature: float64,
    dewPoint: float64,
    humidity: float64,
    icon: string,
    precipIntensity: int64,
    precipProbability: int64,
    pressure: float64,
    summary: string,
    temperature: float64,
    time: int64,
    visibility: int64,
    windBearing: int64,
    windSpeed: float64
    },
  daily: {
    data: 1 * {
      apparentTemperatureMax: float64,
      apparentTemperatureMaxTime: int64,
      apparentTemperatureMin: float64,
      apparentTemperatureMinTime: int64,
      cloudCover: int64,
      dewPoint: float64,
      humidity: float64,
      icon: string,
      moonPhase: float64,
      precipIntensity: float64,
      precipIntensityMax: float64,
      precipIntensityMaxTime: int64,
      precipProbability: float64,
      precipType: string,
      pressure: float64,
      summary: string,
      sunriseTime: int64,
      sunsetTime: int64,
      temperatureMax: float64,
      temperatureMaxTime: int64,
      temperatureMin: float64,
      temperatureMinTime: int64,
      time: int64,
      visibility: float64,
      windBearing: int64,
      windSpeed: float64
      }
    },
  flags: {isd_stations: 5 * string, sources: 1 * string, units: string},
  hourly: {
    data: 24 * {
      apparentTemperature: float64,
      cloudCover: ?int64,
      dewPoint: float64,
      humidity: float64,
      icon: string,
      precipIntensity: float64,
      precipProbability: float64,
      precipType: ?string,
      pressure: float64,
      summary: string,
      temperature: float64,
      time: int64,
      visibility: float64,
      windBearing: int64,
      windSpeed: float64
      },
    icon: string,
    summary: string
    },
  latitude: float64,
  longitude: float64,
  offset: int64,
  timezone: string
  }"""