[TASK] Improve messages for skipped tests

Some messages are wrong, some not informative enough.

Change-Id: I7fa8521730396373ed6aa1daa83dd7864f05efc2
Resolves: #50218
Reviewed-on: https://review.typo3.org/22442
Reviewed-by: Oliver Klee
Tested-by: Oliver Klee
[TASK] Avoid calls to deprecated functions from 4.5 to 6.2

Class mediumDoc is replaced by bigDoc as it got deprecated in 6.1.

Change-Id: I1518cdbec43683c42d824f674259c31f991dff9a
Resolves: #49774
Reviewed-on: https://review.typo3.org/22446
Reviewed-by: Oliver Klee
Tested-by: Oliver Klee
[TASK] Rename TestFinder::findTestCaseFilesDirectory

Rename TestFinder::findTestCaseFilesDirectory to
TestFinder::findTestCaseFilesInDirectory

Change-Id: Ic56a20e5c05f578765d01b321c31804e818f0b33
Resolves: #36999
Reviewed-on: https://review.typo3.org/22449
Tested-by: Oliver Klee
Reviewed-by: Oliver Klee
[FEATURE] Add PHPUnit error handler as default

If the default TYPO3 error handler is enabled the result of any test could
be falsified because some errors might not be raised. PHPUnit tests for an
existing error handler and only sets its own if nothing was set before. So
we have to enforce the PHPUnit error handler to catch all errors.

Change-Id: I89850ca5f0630231611bf28b5563dbed8df51256
Resolves: #50226
Reviewed-on: https://review.typo3.org/22456
Reviewed-by: Oliver Klee
Tested-by: Oliver Klee
[TASK] Update PHPUnit to 3.7

Replace the PEAR version with a composer installation

Change-Id: I18158a6350494392e3c93d7d12ff0ee975f7efc8
Resolves: #41058
Reviewed-on: https://review.typo3.org/22458
Reviewed-by: Oliver Klee
Tested-by: Oliver Klee