Improve error for sequence with lowercase characters #1041
Improve error for sequence with lowercase characters #1041

Fix #1041
jairideout/scikit-bio,jdrudolph/scikit-bio,gregcaporaso/scikit-bio,corburn/scikit-bio,anderspitman/scikit-bio,kdmurray91/scikit-bio,corburn/scikit-bio,jairideout/scikit-bio,jdrudolph/scikit-bio,gregcaporaso/scikit-bio,kdmurray91/scikit-bio,anderspitman/scikit-bio