Improve install space required estimation (#1224048)

The problem was that 35% add is not enough on the smaller installations.
That result in crash on RPM transaction check. RPM required more space
than we have.
This problem was consulted with RPM team and this is result.
The RPM rounding size of files to fragment size (default 4KiB) for
better estimation also they are required package header size * 4 for RPM
DB.

We don't have header size or file size in the installation so I'm trying
to simulate worst case scenario for file rounding and using 2KiB for
every file to get something like RPM DB space required.
Also 10% is add to all this as a safeguard.

Seems as stable assumption right now.
+
Improved logging for packaging.

Resolves: rhbz#1224048

pyanaconda/packaging/dnfpayload.py

@@ -71,6 +71,12 @@
              '/tmp/product/anaconda.repos.d']
 YUM_REPOS_DIR = "/etc/yum.repos.d/"
 
+# Bonus to required free space which depends on block size and rpm database size estimation.
+# Every file could be aligned to fragment size so 4KiB * number_of_files should be a worst
+# case scenario. 2KiB for RPM DB was acquired by testing.
+# 6KiB = 4K(max default fragment size) + 2K(rpm db could be taken for a header file)
+BONUS_SIZE_ON_FILE = Size("6 KiB")
+
 _DNF_INSTALLER_LANGPACK_CONF = DNF_PLUGINCONF_DIR + "/langpacks.conf"
 _DNF_TARGET_LANGPACK_CONF = "/etc/dnf/plugins/langpacks.conf"
 
@@ -115,8 +121,9 @@ def reasonable_mpoint(mpoint):
                    # for root we need to take in count both download and install size
                    if ((key != root_mpoint and val > requested)
                    or val > requested_root) and reasonable_mpoint(key)}
-    log.debug('Estimated size: download %s & install %s - df: %s', requested,
-              (requested_root - requested), df)
+    log.debug('Input mount points: %s', df)
+    log.debug('Estimated size: download %s & install %s', requested,
+              (requested_root - requested))
     log.info('Sufficient mountpoints found: %s', sufficients)
 
     if not len(sufficients):
@@ -555,23 +562,38 @@ def spaceRequired(self):
             if key.startswith('/') and ((root_mpoint + new_key) not in valid_points):
                 valid_points[root_mpoint + new_key] = val.format.freeSpaceEstimate(val.size)
 
-        m_points = _pick_mpoint(valid_points, download_size, size)
-        if not m_points or m_points == root_mpoint:
+        m_point = _pick_mpoint(valid_points, download_size, size)
+        if not m_point or m_point == root_mpoint:
             # download and install to the same mount point
             size = size + download_size
-        log.debug("Instalation space required %s for mpoints %s", size, m_points)
+            log.debug("Install + download space required %s", size)
+        else:
+            log.debug("Download space required %s for mpoint %s (non-chroot)", download_size, m_point)
+            log.debug("Installation space required %s", size)
         return size
 
     def _spaceRequired(self):
         transaction = self._base.transaction
         if transaction is None:
             return Size("3000 MB")
 
-        size = sum(tsi.installed.installsize for tsi in transaction)
-        # add 35% to account for the fact that the above method is laughably
-        # inaccurate:
-        size *= 1.35
-        return Size(size)
+        size = 0
+        files_nm = 0
+        for tsi in transaction:
+            # space taken by all files installed by the packages
+            size += tsi.installed.installsize
+            # number of files installed on the system
+            files_nm += len(tsi.installed.files)
+
+        # append bonus size depending on number of files
+        bonus_size = files_nm * BONUS_SIZE_ON_FILE
+        size = Size(size)
+        # add another 10% as safeguard
+        total_space = (size + bonus_size) * 1.1
+        log.debug("Size from DNF: %s", size)
+        log.debug("Bonus size %s by number of files %s", bonus_size, files_nm)
+        log.debug("Total size required %s", total_space)
+        return total_space
 
     def _isGroupVisible(self, grpid):
         grp = self._base.comps.group_by_pattern(grpid)
@@ -688,7 +710,7 @@ def install(self):
                 _failure_limbo()
 
         pkgs_to_download = self._base.transaction.install_set
-        log.info('Downloading packages.')
+        log.info('Downloading packages to %s.', self._download_location)
         progressQ.send_message(_('Downloading packages'))
         progress = DownloadProgress()
         try: