[Error] [ipython] Use print directly instead of builtin warnings module to prevent being supressed

[archibate]

Related issue = #677 (comment)

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It seems that if I use IPython (ti repl), the warning is depressed. If I use raw Python shell (python), the warning is shown.
So IPython is setting warnings.filterwarnings('ignore') on their own? Anyway, the built-in warning system seems unreliable.
Let's switch to standard print for warning instead.

[codecov]

Codecov Report

Merging #1969 into master will increase coverage by 0.07%.
The diff coverage is 77.77%.

@@            Coverage Diff             @@
##           master    #1969      +/-   ##
==========================================
+ Coverage   43.64%   43.72%   +0.07%     
==========================================
  Files          45       45              
  Lines        6225     6221       -4     
  Branches     1106     1105       -1     
==========================================
+ Hits         2717     2720       +3     
+ Misses       3334     3328       -6     
+ Partials      174      173       -1     

Impacted Files	Coverage Δ
python/taichi/lang/meta.py	64.00% <0.00%> (+1.17%)	⬆️
python/taichi/misc/util.py	20.54% <100.00%> (+2.26%)	⬆️

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[yuanming-hu]

Thanks! I don't exactly know what happened with IPython, but it works on my end.