No judge shall sit in any cause, except to hear a motion to change the venue, if interested in its determination, or if the judge might be excluded for bias from acting therein as a juror. If there is no other judge of the court or district, the judge shall grant a change of the venue when, upon a motion therefor, the interest or bias shall be made to appear, unless before the motion is heard the governor shall have assigned another judge to try such cause. The venue may be changed upon the sole judge’s motion upon deeming it improper to sit in the cause.