py2: demo/kpidemo.*: Adjust it for python2

- fix import for urlopen
- there is no subfigures support on matplotlib2 -> use two separate figures.
  this leads to two spearate windows for kpidemo.py, but at least it works somehow.
- omit ConciseDateFormatter - it is present only in matplotlib3
- refresh the notebook

demo/kpidemo.py

 #!/usr/bin/env python
+# -*- coding: utf-8 -*-
 """kpidemo - plot KPIs computed from enb.xlog
 
 Usage: kpidemo <time period> <enb.xlog uri>
@@ -17,7 +18,7 @@ from matplotlib import ticker
 from datetime import datetime, timedelta
 
 import sys
-from urllib.request import urlopen
+from urllib2 import urlopen
 
 
 @func
@@ -123,8 +124,8 @@ def main():
     # all QCIs and does not have uncertainty. QCIs for which throughput data is
     # all zeros are said to be silent and are not plotted.
 
-    fig = plt.figure(constrained_layout=True, figsize=(12,8))
-    facc, fthp = fig.subfigures(1, 2)
+    facc = plt.figure(1)
+    fthp = plt.figure(2)
     figplot_erab_accessibility  (facc, vtau, vInititialEPSBEstabSR, vAddedEPSBEstabSR, tperiod)
     figplot_eutran_ip_throughput(fthp, vtau, vIPThp_qci, tperiod)
     plt.show()
@@ -210,9 +211,9 @@ def plot_per_qci(ax, vtau, v_qci, label):
 # fmt_dates_pretty instructs axis to use concise dates formatting.
 def fmt_dates_pretty(axis):
     xloc = mdates.AutoDateLocator()
-    xfmt = mdates.ConciseDateFormatter(xloc)
+    #xfmt = mdates.ConciseDateFormatter(xloc)   # only in matplotlib > 2
     axis.set_major_locator(xloc)
-    axis.set_major_formatter(xfmt)
+    #axis.set_major_formatter(xfmt)
     axis.set_minor_locator(ticker.AutoMinorLocator(5))