"Error: Trace type must be one of the following:" produces an unordered list of trace types

If a user supplies an incorrect trace type the error message includes an unordered list of trace types that is difficult to read

#> Loading required package: ggplot2
#> 
#> Attaching package: 'plotly'
#> The following object is masked from 'package:ggplot2':
#> 
#>     last_plot
#> The following object is masked from 'package:stats':
#> 
#>     filter
#> The following object is masked from 'package:graphics':
#> 
#>     layout
iris %>% 
  plot_ly() %>% 
  add_trace(x = ~Petal.Length,
            y = ~Petal.Width,
            type = "non-existant-trace-type")
#> Error: Trace type must be one of the following: 
#> 'scatter', 'bar', 'box', 'heatmap', 'histogram', 'histogram2d', 'histogram2dcontour', 'contour', 'scatterternary', 'violin', 'funnel', 'waterfall', 'image', 'pie', 'sunburst', 'treemap', 'funnelarea', 'scatter3d', 'surface', 'isosurface', 'volume', 'mesh3d', 'cone', 'streamtube', 'scattergeo', 'choropleth', 'scattergl', 'splom', 'pointcloud', 'heatmapgl', 'parcoords', 'parcats', 'scattermapbox', 'choroplethmapbox', 'densitymapbox', 'sankey', 'indicator', 'table', 'carpet', 'scattercarpet', 'contourcarpet', 'ohlc', 'candlestick', 'scatterpolar', 'scatterpolargl', 'barpolar', 'area'

issue 中没有指定文件或测试。复现无效 type 示例，然后定位组装 trace 类型错误的代码；当受支持的 trace 类型以易读的列表呈现，且无效类型错误仍然清晰时，即表示完成。