Converting a VCF into a FASTA given a reference with Python, R
You can whip up something quite easily in Python using pyfaidx, which allows you to access a FASTA file by genomic coordinates. So you'd just have to pull the coordinates from the VCF to get the sequence, then output in FASTA format with whatever unique identifier for each sequence you want to use.

Edit: The FastaVariant class is new in pyfaidx, I hadn't seen it before. It makes this even easier, as you won't have to manually mess with the VCF to get the positions. Something like the following should work:

consensus = FastaVariant('yourgenome.fasta', 'variants.vcf.gz', het=True, hom=True)

out = open("variants.fasta", "w")

for chrom in consensus.keys:
    for var in consensus[chrom].variants_sites:
        record = consensus[chrom][var-1:var]
        print(record, file=out)

out.close()