Python 2, 48 43 bytes

Returns 0 on error.

lambda m,n:m/n and[m/n]*(n-m%n)+m%n*[m/n+1]

Try it online!

41 bytes (with @xnor's trick)

Throws ValueError on error.

lambda m,n:[m/n or _]*(n-m%n)+m%n*[m/n+1]

Try it online!

Python 2, 48 43 bytes

Returns 0 on error.

lambda m,n:m/n and[m/n]*(n-m%n)+m%n*[m/n+1]

Try it online!

41 bytes (with @xnor's trick)

Throws NameError on error.

lambda m,n:[m/n or _]*(n-m%n)+m%n*[m/n+1]

Try it online!

Python 2, 48 45 bytes

Returns 0 on error.

lambda m,n:m/n and[m/n+1]*(m%n)+[m/n]*(n-m%n)

Try it online!

Python 2, 48 43 bytes

Returns 0 on error.

lambda m,n:m/n and[m/n]*(n-m%n)+m%n*[m/n+1]

Try it online!

41 bytes (with @xnor's trick)

Throws ValueError on error.

lambda m,n:[m/n or _]*(n-m%n)+m%n*[m/n+1]

Try it online!

Python 2, 48 bytes

Returns 0 on error.

lambda m,n:m/n and[m/n+(i<m%n)for i in range(n)]

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Python 2, 48 45 bytes

Returns 0 on error.

lambda m,n:m/n and[m/n+1]*(m%n)+[m/n]*(n-m%n)

Try it online!