Certain high precision central longitudes can cause the Mercator projection to have nonsensical bounds

[mhearne-usgs]

On my system (Ubuntu 20.04.4 LTS) and on a colleagues Mac, the script below gives the following results:

Failure to create valid mercator projection boundaries with -169.40000000042403
Successfully created valid mercator projection boundaries with -169.4

I am using Cartopy 0.25.0, he is using 0.24.1.

I'm going to try reducing the precision as a workaround all the time, but I'll need to do lots of tests since I'm making maps in an automated system.

import cartopy.crs as ccrs
import matplotlib.pyplot as plt
import numpy as np

if __name__ == "__main__":
    bounds = (
        -172.32916666697352,
        -166.4708333338745,
        50.50416666824549,
        54.11250000143449,
    )
    xmin, xmax, ymin, ymax = bounds
    clon = (xmin + xmax) / 2
    clat = (ymin + ymax) / 2
    if xmax < 0 and xmax < xmin:
        clon = (xmin + (xmax + 360)) / 2

    proj = ccrs.Mercator(
        central_longitude=clon,
        max_latitude=ymax,
        globe=None,
    )
    try:
        assert (proj.boundary.bounds[2] - proj.boundary.bounds[0]) > 1
    except AssertionError:
        print(f"Failure to create valid mercator projection boundaries with {clon}")
    new_clon = np.round(clon, decimals=2)
    proj = ccrs.Mercator(
        central_longitude=new_clon,
        max_latitude=ymax,
        globe=None,
    )
    print(f"Successfully created valid mercator projection boundaries with {new_clon}")