Error messages using @assert need to be turned into normal exceptions

[akabla]

We deal with many errors in parameters with an @assert macro. For instance:
@assert hastime(d) "Data without time information cannot be resampled."

@assert may be disabled with certain optimisations, and therefore not appropriate for this usage.
https://docs.julialang.org/en/v1/base/base/#Base.@assert

It would be more appropriate to reserve @assert for debugging purposes only, and use proper exceptions for error message supposed to be helpful to the user.

This page may be useful:
https://scls.gitbooks.io/ljthw/content/_chapters/11-ex8.html

[moustachio-belvedere]

Important issue, but I think this is duplicated:

#81

[akabla]

indeed! let me close this here - no need to have it twice.