get_djuser_name error specificity

[CBroz1]

The following error message could be more specific

spyglass/src/spyglass/common/common_lab.py

Lines 135 to 139 in 6b4ff10

	if len(query) != 1:
	raise ValueError(
	f"Could not find name for datajoint user {dj_user}"
	+ f" in common.LabMember.LabMemberInfo: {query}"
	)

The error message is written assuming the case of len(query) == 0, but a dj user name could exist twice in this table, causing confusion