Fix HRV area definition tests

[mraspaud]

Some tests were failing with the newer pyproj.

The main problem was that pyproj is now converting floats to ints when possible for the projection parameters, hence triggering some errors.

• Tests passed
• Passes flake8 satpy

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (master@0f76aea). Click here to learn what that means.
The diff coverage is 100%.

@@            Coverage Diff            @@
##             master     #903   +/-   ##
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  Coverage          ?   84.84%           
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  Files             ?      171           
  Lines             ?    25297           
  Branches          ?        0           
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  Hits              ?    21464           
  Misses            ?     3833           
  Partials          ?        0

Impacted Files	Coverage Δ
satpy/tests/reader_tests/test_seviri_l1b_hrit.py	98.91% <100%> (ø)
satpy/tests/test_config.py	87.34% <100%> (ø)
satpy/readers/utils.py	75.23% <100%> (ø)

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[sfinkens]

Should h be converted to float here as well? https://github.com/pytroll/satpy/blob/master/satpy/readers/utils.py#L138

And one nitpick: Maybe it would be more clear to explicitly convert the proj dict items to float instead of dividing them by 1000. .