Added pyqt5 to requirements

Makefile

@@ -63,7 +63,7 @@ endif
 	@${PYTHON} -c 'import PyQt5' >/dev/null 2>&1 || \
 		{ echo "PyQt 5.4+ required. Install it and try again. Aborting"; exit 1; }
 
-env : | reqs
+env : requirements.txt | reqs
 ifndef NO_VENV
 	@echo "Creating our virtualenv"
 	${PYTHON} -m venv env

requirements.txt

@@ -1,5 +1,6 @@
+pyqt5>=5.15.1
 Send2Trash>=1.3.0
 sphinx>=1.2.2
 polib>=1.0.4
 hsaudiotag3k>=1.1.3
-distro>=1.5.0
+distro>=1.5.0