dtype validation from 24024

[jbrockmendel]

Fix tests in tests_datetimelike that are passing incorrect freqs

Implements some but not all of the dtype-validation tests in #24024; retains extant error messages instead of those raises in 24024.

Some stream-lining could be done if we change the behavior of validate_tz_from_dtype, which includes:

            try:
                dtype = DatetimeTZDtype.construct_from_string(dtype)
            except TypeError:
                # Things like `datetime64[ns]`, which is OK for the
                # constructors, but also nonsense, which should be validated
                # but not by us. We *do* allow non-existent tz errors to
                # go through
                pass

We could merge _validate_dt64_dtype into this really easily by changing these lines to just call dtype = pandas_dtype(dtype), but that would raise on non-existent tz, which current policy allows.

[codecov]

Codecov Report

Merging #24478 into master will decrease coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master   #24478      +/-   ##
==========================================
- Coverage   92.32%   92.32%   -0.01%     
==========================================
  Files         166      166              
  Lines       52298    52305       +7     
==========================================
+ Hits        48285    48288       +3     
- Misses       4013     4017       +4

Flag	Coverage Δ
#multiple	90.74% <100%> (-0.01%)	⬇️
#single	43.07% <66.66%> (ø)	⬆️

Impacted Files	Coverage Δ
pandas/core/reshape/tile.py	94.82% <100%> (ø)	⬆️
pandas/core/arrays/datetimes.py	97.59% <100%> (-0.67%)	⬇️

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[codecov]

Codecov Report

Merging #24478 into master will decrease coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master   #24478      +/-   ##
==========================================
- Coverage   92.32%   92.31%   -0.01%     
==========================================
  Files         166      166              
  Lines       52328    52335       +7     
==========================================
+ Hits        48310    48313       +3     
- Misses       4018     4022       +4

Flag	Coverage Δ
#multiple	90.73% <100%> (-0.01%)	⬇️
#single	43.05% <66.66%> (ø)	⬆️

Impacted Files	Coverage Δ
pandas/core/reshape/tile.py	94.82% <100%> (ø)	⬆️
pandas/core/arrays/datetimes.py	97.77% <100%> (-0.67%)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 3f83627...24755d6. Read the comment docs.

[jreback]

can you merge master

[jreback]

lgtm ping on green.

[jbrockmendel]

ping