Remove unused imports. Explicitly import a few deep imports.

gui/qt/password_dialog.py

@@ -23,8 +23,9 @@
 # CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 # SOFTWARE.
 
+from PyQt5.QtCore import Qt
 from PyQt5.QtGui import *
-from PyQt5.QtCore import *
+from PyQt5.QtWidgets import *
 from electrum.i18n import _
 from .util import *
 import re